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Author Topic: Let's talk about cams.  (Read 13607 times)

ace.cafe

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Let's talk about cams.
« on: January 03, 2009, 03:15:00 PM »
After a post on another thread by Jon Applegate about cams, I thought it might be good to take a look at cams for the Bullet.

First, let's find out what cams do.
Cams are actuators for the valves. They translate rotary motion into linear motion. So, as a cam is turned by the crankshaft gear, it has a "cam lobe" which is ground eccentric to the centerline, and  moves the valve lifter up and down, according to the designer's intentions for the expected application of the engine.
This is the basic function of cams in an engine.

In the world of increasing performance in an engine, cams are often discussed as a central theme. After all, the cams control the valves, and the valves control the breathing, and the breathing controls the power. So, it stands to reason that cams are a big part of making an engine produce more power.

How do cams control the breathing?
Well, this is simple. They are in control of when the valve opens and when the valve closes. The longer the valve can remain open, the more flammable mixture can enter the cylinder for burning, and the more power can be produced. And the higher the valve can be lifted off its seat, the more mixture can come into the engine, as well.
So, this defines our 2 main areas of concern with cams. "Duration" and "Lift". These combine to regulate our breathing in the engine. For performance purposes we want  long duration to keep that valve open as long as possible, and high lift to open that valve as far as we can. Doing both things to try to maximize the "gulp of air" that we are pulling down the port.

So, what's the big deal, let's just open them up wide open and leave them open forever!
Well we can't do that, because the engine has cycles for intake, compression, power, and exhaust, so they need to be closed sometimes, and mechanical restrictions in the engine design will dictate how far they can be opened.

And this is where the "art and science" of cam design comes into play. 
How much can we do with our particular engine design, for our particular purposes?
That's the big question.

First we need to look at the effects that come from longer duration.
Many people may think that valves just open at TDC(top-dead-center) on the intake stroke, and close at BDC(bottom-dead-center) on the intake stroke. It's easy to assume that the piston works like a hypodermic syringe, and only fills when the piston is descending. And, for a long time, that's what people thought, and how they designed intake systems. TDC to BDC breathing cycle.
Then as engineering became more sophisticated, better methods were developed.
For example, we can't open the valves instantly from fully closed to fully open. They require some "ramping", so that we don't lose control of them from insane acceleration rates, which the valve springs can't handle. So, they need  some time to get open, and some time to close down. So, we open them a bit before TDC, and close them a bit after BDC. This way, they are open pretty much fully for the entire TDC to BDC intake stroke. That's a good start.
So, what happens when we try to have them open even more than that?
Well, then we have some interactions going on that we need to consider.
The first one is that we need to understand that the air coming into the engine has a mass and a flow rate curve. When we draw the piston down, the air in the port doesn't immediately accelerate to full velocity. It begins to speed up, and there is a bit of a time lag before it's flowing at full velocity. And on the other end, even after the piston stops going down, the air still is moving into the cylinder because it has some inertial energy of its motion that causes it to still keep coming into the cylinder, because of this time lag of the mixture velocity curve. So, some of the filling of the cylinder is actually accomplished after BDC, when the piston is no longer pulling it down. After BDC, the air is coming in by virtue of it's own inertia, on the tail end of the flow curve, which is lagged behind the motion curve of the piston movement.
So, we can utilize this additional fill ing potential by NOT closing the valve at BDC. We want to keep it open longer, so that we can capture the incoming mixture that is still flowing in by inertia. How much later can we close it? Well that depends on alot of things, but we may get to that later.
Ok, now that we know that we can close the valve later than we thought, to attain more performance, what about opening it earlier?
Well we can do that too. But how?
If we open the valve before TDC, isn't the ascending piston going to push air back up the intake port? Well, yes it could, but we have a way around that.
The piston slows down as it approaches TDC and BDC, and has what is known as a "Dwell period" where very little vertical motion occurs as it passes the top and bottom of the stroke. This is due to the circular motion of the crank, and at top and bottom of the stroke, the crank is moving horizontally(primarily) and not vertically, so the piston is hardly even moving at all for about 20 degrees on either side of TDC and BDC. So, this is an area where we can work in.
But, how do we get anything coming in, when the piston isn't pulling down like a syringe?
The answer to this involves the exhaust. On the exhaust stroke, which is going on just prior to the intake stroke, the exhaust valve is open, and there is a rush of exhaust gas flowing out the exhaust port. If the exhaust flow speed is fast enough, it causes a low pressure zone around the intake valve, and if we open the intake valve at the right point, we can "hitch a ride" on this exhaust flow to start pulling some of our intake mixture into the cylinder while both valves are open around TDC. This is called "cam overlap", where both valves are open at the same time.  Yes, some intake mixture goes out the exhaust port, but this cool mixture helps to cool the exhaust valve a little bit, and the main benefit is to start the intake flow curve happening a bit earlier than it normally would. Of course there is a limit to this, and if you open the intake valve too early on the exhaust stroke, you will have exhaust backing out the intake port. Timing is important on the opening and the closing valve events, so that you can get what you want, and avoid what you don't want.

So,we've looked at ways we can open the intake valve eariler, and close it later, to get addtional mixture into the engine. And we've briefly looked at cam overlap, and what it does.

I'm continuing to write this, but I'm posting it up in sections as I go along. More to come in a few minutes.
« Last Edit: January 03, 2009, 03:40:35 PM by ace.cafe »
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ace.cafe

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Re: Let's talk about cams.
« Reply #1 on: January 03, 2009, 03:45:22 PM »
Ok, now to continue, and discuss about how this applies to the Bullet.

The Bullet is a long stroke, long rod, engine design.
This type of engine has a pretty large amoung of "dwell period" around TDC and BDC. We can work with this to our advantage.
By using a later intake valve closing timing, we can use the inertia of the mixture after BDC to really assist our cylinder filling, because the piston isn't starting to come back up right away on the compression stroke. In fact we can leave it open for nearly  75 degrees after BDC, if we can use that properly.
2 things need to be attended-to, in order for this to work.
We need to have sufficient intake air-speed inertia, so that the air will still be rushing in, or else there is no point to leaving the valve open. So that means that our intake port cannot be too big, so as to cause a slowing of airspeed in the port. We NEED to have high port speeds for this, or it doesn't work. This is why it is so important to not enlarge the port too big. Enlarging increases potential mass flow, but kills the air velocity in the port, and we need that for late intake valve closing timing to work right.
The second thing is that with late intake valve closing timing, the piston is ascending, and trying to build compression. If the intake mixture speed that is still trying to fill the last bit of mixture into the cylinder is overcome by the attempt of the piston to build compression, the mixture starts to get pushed back up the intake port, and we get reversion, lower compression, and is generally counterproductive.
So, the ideal is to close the valve at the exact point where the intake mixture flow is just still slightly higher than the building of compression. Then close it down tight to get the maximum fill. In practice, some building of compression will be lost in this process, so that's why it is critical to use a higher-compression piston with cam timing like this. We need a higher compression piston to help us get back any compression that may have been lost with the late valve timing, in the remaining part of the compression stroke.

Ok, now let's look at the earlier intake valve opening timing for the Bullet.
The earlier intake valve opening event relies on rapid exhaust speeds to start pulling intake mixture in, as the intake valve is opened at the tail end of the exhaust cycle, during the overlap period.
Unfortunately, the Bullet exhaust port and exhaust pipe is oversize in stock form, and does not provide us with much exhaust speed to speak of. And there's not much we can do about it, because it's already too big to start with.
So, early intake valve opening timing does not do us much good with the Bullet engine.
It works ok at higher rpms, and that's where wide valve overlaps are at their best, but the problem is that our Bullets are low-revving engines which are rpm limited by piston speeds and strength of the crank and rod in the bottom end. So, we can't really access these higher rpms unless we are racing, or have the expensive crank and rod package that most of us don't have or can't afford.

However, the cam designers are designing race cams. They expect high-rpm use with their cams. So, they build in alot of early intake valve opening timing for wide overlap, with the idea that we will all be riding around at 7000 rpms, which is not the case for 99% of us.
The result of this is that we get the very "soft and spongy" feel of the engine in the low and midrange rpms, that comes along with too much cam overlap timing, and we can't access the top rpms where these cams really work well at.
So we get a spongy-feeling engine with power losses down low, and only can access about 1000-1500 rpms of the area where the cams will be working right.
This translates into "less than desirable" road application, and it explains why the cams are not real popular with Bullet owners who don't race.
All of the current performance or racing cams for the Bullet today, no matter where you get them, or who makes them, suffer from too much overlap timing for a good road application. They sacrifice too much of the low and midrange torque, for a small slice of power that we can access at the top end of the rpm scale with a standard Bullet bottom end.
That's the long and short of it, and none of the current cam designers have decided to really address this matter for normal Bullet road riders with standard-issue bottom ends. Because you see, what sells race cams is max hp and max rpm figures. They don't ever even discuss what happens to your midrange, because top end power is all they are after.

What's needed for the Bullet is a cam set with a late intake valve closing timing, and a more moderate intake valve opening timing, along with an exhaust cam with earlier exhaust valve closing time. This will shorten the overlap period on both ends, improve the cylinder trap, and provide good top-rpm power in the ranges where we can access it, and not lose any of the low and midrange torque that we need for our road riding. Use a cam set like this with the hi-compression piston and a properly ported head with a multi-angle valve job, free-flow exhaust, and good carburetion and free-flow intake filter,with about 4 degrees retarded ignition timing, and it should put you over 30hp at the rear wheel, and still allow use of the standard bottom end. And there would be no losses anywhere in the rpm range, compared to what you have now. It would be all gain, and no sacrifice at any rpm.. It's a cam set to produce torque and power in the ranges that a standard Bullet bottom-end can access.

That's about it for now.

Thread is open for comments and questions.
 ;D
« Last Edit: January 03, 2009, 04:54:06 PM by ace.cafe »
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Vince

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Re: Let's talk about cams.
« Reply #2 on: January 03, 2009, 05:07:29 PM »
     Ace, I would appreciate it if you would go into the flow or wave dynamics of exhaust technology, particularly as it applies optimizing combustion chamber filling. Most Enfield owners go to a free flowing exhaust. However,  more modern systems are using 2-cycle expansion chamber technology and flow formulas for the exhaust systems to aid scavenging as well as well as intake.
     In high-revving engines  this type of exhaust allows for wilder cam timing yet still manage to produce  a relatively wide power band. Taken to extremes these exhaust systems even have variable valving in the system itself to change resonance frequencies at different RPM.
     How would any of this technology benefit a low revving engine such as the Enfield? Would a tuned expansion chamber allow for more effective use of existing cams and port sizes?

Cabo Cruz

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Re: Let's talk about cams.
« Reply #3 on: January 03, 2009, 05:23:09 PM »
Vince, I join you -- and othres --  in anticipation of the next installment by The Doctor, er, our dear colleague, Ace.  And, Jim (HRAB) forgive me for usurping the moniker of your favorite racer, THE DOCTOR, or #46!
Long live the Bullets and those who ride them!

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ace.cafe

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Re: Let's talk about cams.
« Reply #4 on: January 03, 2009, 06:07:54 PM »
     Ace, I would appreciate it if you would go into the flow or wave dynamics of exhaust technology, particularly as it applies optimizing combustion chamber filling. Most Enfield owners go to a free flowing exhaust. However,  more modern systems are using 2-cycle expansion chamber technology and flow formulas for the exhaust systems to aid scavenging as well as well as intake.
     In high-revving engines  this type of exhaust allows for wilder cam timing yet still manage to produce  a relatively wide power band. Taken to extremes these exhaust systems even have variable valving in the system itself to change resonance frequencies at different RPM.
     How would any of this technology benefit a low revving engine such as the Enfield? Would a tuned expansion chamber allow for more effective use of existing cams and port sizes?

Hi Vince,
Wave tuning is something that is generally thought of as very technical and mysterious, but it's really a very simple principle.
It is all just the timing of the sound waves as they move down the exhaust port and reflect back up. That's really all there is to it.
You make the pipe a certain length which is the right length to time the reflected sound wave to come back into the combustion chamber at the point when the valve is open for the effect you want it to have.

From a road riding view, this is not alot of use to us, because the pipe length tuning is for a specific rpm, and the harmonic intervals of that specific rpm.
So, you could tune your pipe for max hp rpm, but that's pretty much the only place it's going to work, or maybe half that rpm also, as the next lower harmonic. Beyond that, it's not going to really do anything. It pretty much primarily works best on an open pipe without a muffler. This is good for racers, but it's of dubious benefit for road work, and many/most of the road exhausts have wave-breakers in the form of slant tips or baffles, or even anti-reversion cones to break these effects on street machines. Sometimes you see the reversion effects as a "stand-off" of gas mist outside the carburetor throat, as the wave reversion from the exhaust passes thru the open exhaust valve and thru the open intake valve during the overlap period at idle, and blows this mixture out the carb, where it stands-off for a short period and is then sucked back into the intake.

An expansion chamber works in a similar way to the end of an open exhaust pipe.
When the exhaust "sees" a big change in air pressure, such as an opening of a pipe or an wide-diameter expansion chamber, there is an "impedance mismatch" which reflects the sound wave back up the pipe. With the expansion chamber, this can be placed fairly close to the exhaust port, without having a super short overall exhaust pipe length. This causes rapid reflection behavior which should be timed to the engine to give best results at a certain rpm range. This is what's commonly called being "on the pipe" in 2-stroke vernacular. As you noted, this would generally be productive for higher revving machines, since they need quick reflections at those high rpms. We don't have that. We need longer pipes to get our results, because we are operating at slower rpms, and thus the reflections don't want to be that quick.
In any case, these kinds of mods are very "tuned" to specific rpm ranges of the engine, and in a Bullet where wide torque band is the hallmark of our engine's ridabiity characteristics, we would be better served with a normal exhaust system that doesn't get "peaky" at any particular range, but instead gives a broad and flat torque curve. At least, for road riding that would be preferred.

Variable valve timing is a whole other can of worms that has alot of good benefits, but we'll never see them in our Bullets. The main function of VVT is to reduce overlap at lower throttle openings for best torque in the lower and midrange rpms, and widen overlap at higher throttle openings to take advantage of where the overlap can give benefits. It overcomes the issues seen in fixed valve timing at different rpm and load conditions, and provides improved efficiency, fuel economy, and power, with enhanced ridability throughout the range of rpms and throttle settings. And yes, since the valve timing will be varied, it will give varied result in the wave behavior in the exhaust and intake systems as well. Some engines, such as the MV Agusta, even vary the length of the intake tracts via motorized velocity stack systems, to optimize the intake wave tunings for various engine requirements.
This is all computerized stuff, and is way beyond anything we could dream about with the Bullet.

Our engines would benefit more from what you see in the Harley-Davidson category, which is closer that what our engine design is like. In fact, our Bullet is rather like "half" of the old Sportster engine, with hemi chamber, 2-valve, pushrod, long stroke, aircooled design. Really quite similar.

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Vince

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Re: Let's talk about cams.
« Reply #5 on: January 03, 2009, 06:41:49 PM »
     Ace, when I asked about variable valves I meant that some modern bike have a valving mechanism actually in the pipe after and in addition to the exhaust valve. It does not completely block the port but rather is a relatively small restriction in the port. This restriction changes with RPM and throttle setting with more restriction at low RPM and less at high RPM.
     Two stroke engines drive this with gears driven by a Sprag clutch. Four stroke engines are usually computer/servo controlled. Less refined systems could be throttle cable controlled.
     Would this be of help or even be worth the trouble?

ace.cafe

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Re: Let's talk about cams.
« Reply #6 on: January 03, 2009, 07:12:11 PM »
     Ace, when I asked about variable valves I meant that some modern bike have a valving mechanism actually in the pipe after and in addition to the exhaust valve. It does not completely block the port but rather is a relatively small restriction in the port. This restriction changes with RPM and throttle setting with more restriction at low RPM and less at high RPM.
     Two stroke engines drive this with gears driven by a Sprag clutch. Four stroke engines are usually computer/servo controlled. Less refined systems could be throttle cable controlled.
     Would this be of help or even be worth the trouble?

Ohhhh!
You mean something like the Yamaha EXUP system. I get it now.

Yes, that is sort of like a carburetor butterfly valve for the exhaust system.
It can work, and I think Yamaha had some good results with that, and I believe that the patent has recently expired on it.

I never experimented with something like that myself.
I suppose if you could rig it up at the right spot, and make a suitable control mechanism for it, you might be able to get something out of it.

In the end, it basically ends up being a "variable diameter exhaust pipe" to a certain degree.
The problem that I see with it is that it happens only over a short part of the exhaust system so speeds are dramatically changed over a short distance, and I'm not sure how great that is for overall results.
But heck, I never tried it, so maybe I'm all wet about that. It might be worth a try.
If these other companies are using it, then there's probably something useful about it, or they wouldn't put it on there.
« Last Edit: January 03, 2009, 07:17:06 PM by ace.cafe »
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Vince

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Re: Let's talk about cams.
« Reply #7 on: January 03, 2009, 07:36:34 PM »
     Thanks Ace! Very interesting  and well expressed!

redcat

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Re: Let's talk about cams.
« Reply #8 on: January 03, 2009, 09:23:06 PM »
Wow! That was the best piece I have read on this site! Thanx Ace....Tony
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PhilJ

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Re: Let's talk about cams.
« Reply #9 on: January 03, 2009, 11:14:42 PM »
Learn - learn - learn - Now my head hurts. ::)

Cabo Cruz

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Re: Let's talk about cams.
« Reply #10 on: January 03, 2009, 11:17:46 PM »
Amen, Phil...   :o
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jonapplegate

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Re: Let's talk about cams.
« Reply #11 on: January 05, 2009, 02:06:33 AM »
  I like to think I know a little about the mysteries of the internal combustion engine and try to keep on top of the tech.
  I stand corrected.
   I stand in awe of both Vince and Ace.
    I gots sum learnin' to do.....
       
  SO, I was wondering about slightly enhanced cams instead of "performance" and "full race" options. Designing a new cam is a little more involved than just adjusting the Duration, Overlap, Lift etc. Would it be easier (less expensive) to design and produce a higher ratio rocker? I don't know the ratio of the RE rockers but say something modest like going from 1.5 to 1.6? And if someone was were going to do this, how about a roller?

ace.cafe

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Re: Let's talk about cams.
« Reply #12 on: January 05, 2009, 03:56:52 AM »
 
       
  SO, I was wondering about slightly enhanced cams instead of "performance" and "full race" options. Designing a new cam is a little more involved than just adjusting the Duration, Overlap, Lift etc. Would it be easier (less expensive) to design and produce a higher ratio rocker? I don't know the ratio of the RE rockers but say something modest like going from 1.5 to 1.6? And if someone was were going to do this, how about a roller?

Hi Jon,
Well, you may be interested to know that I've been discussing this with some other engine builders and Bullet owners that I know, on some private technical forums, for about 3 years.  We have worked on trying to do design improvements in these areas, and every way you look, there are limiting factors. These people in this group I've worked with are some of the most knowledgeable people you are going to come across, and have worked with people like Yoshimura and Jerry Branch.

Let's take a look at the option of increasing the rocker ratio. It's possible to get just a little bit of change, before you angle the pushrods too much. We've looked at that, and at an entire re-design of the rocker system. Even gone so far as to CAD/CAM some designs, and run them thru computer modeling. It's not impossible, but very difficult and costly to get anywhere near where we want to go.
And even if we could get some benefit, the lift amounts needed to get appropriate lift to achieve a true hi-lift valve system that can achieve the cone swirl around the valve head in this hemi chamber is on the order of .650" lift, which is never going to happen in the Bullet. We are stuck with a low-lift system, and even the max attainable is something around .425" lift, which is hell on the valve train and still doesn't get into hi-lift territory.

So, basically I can tell you that this territory has all been covered with a fine tooth comb. Certain things "could" be done, but nobody is about to fork over the amount of money necessary to do them, because there's a very small number of people interested in purchasing such items. and the costs to have them tooled up and made are very high. These ambitious projects are just DOA because of that.

Now, that is not to say that some things can't be done, and I have some answers for you.
The answers are primarily involved with knowing how to maximize what we have to work with, and making the best of it.

These answers revolve around making the best of what we can fit into the Bullet package without heroic efforts that cost beyond what is recoverable, and work in the ranges that a normal Bullet bottom-end can withstand, or even a bit higher with the billet crank and steel rod and alpha bearing big end.
We need to  maximize our low-lift package, and we have duration room to work with.

First of all, we need to be realistic about our goals. We are not going to be a Molnar short-stroke Manx with 150mph capability on the track. We want good streetable performance.

For cams, the best option for street use, while retaining good low and midrange torque is a re-phase of the stock cams, like I mentioned on the other thread. This activity is not for the casual user. This is for somebody who knows how to work an engine.
The stock cam timing, as fitted, are not the same as the original Redditch cams. They have been adjusted to suit the larger port size in the Indian-made head, and give larger burnt-gas-fraction(BGF) so as to be better suited for emission control. They are more suited for TDC to BDC cylinder fill, and thus have reduced power levels compared to the original Redditch engine, and the hp figures bear this out.
It turns out that the Indian-made intake cam is further advanced in it's timing than the original Redditch cam. It's advanced enough that it is on the order of about one tooth difference, about 18 degrees. So, if we retard just the intake cam by one tooth, and leave everything else alone, we can approximately restore the old 1950s Redditch cam timing, and get back up to the Redditch 25hp figure of the old British Bullets.
Now, we have to be careful, because the Indian-made Bullets have cams which seem to vary in timing from one to the next. So, we have to use a degree wheel and dial indicator to check the cam timing with what we've got, so that we can be sure what we are doing is going to work out as we intend. "Assuming" that our cam timing is as expected, we can then retard the intake cam by one tooth, and leave the exhaust cam alone, and restore the original cam timing for more power. BUT, we don't have the small ports of the Redditch Bullet in our head, so we need to install a 8.5:1 hi-compression piston to make this work right with the bigger ports in the Indian head, due to lower port speeds in the larger head, so we can recover the lost early compression building involved with the later cam timing.
Ok, that sounds pretty good, but we can go further.
If we use the CMW adjustable cam timing pinion, we can then advance both the intake and exhaust cams by 4.5 degrees, and make the intake cam closing timing a little bit better for the big Indian-made head port, and also close the exhaust cam a little earlier to limit the overlap on the exhaust side for better cylinder trap, since we can't really use all that overlap with our oversize ports.
These mods can get us up into the 30hp and 30ft/lbs torque area at the rear wheel, assuming we have already done the freeflow intake and exhaust system changes and re-jetted.
In fact, this cam timing change can get us within 1hp of the Performance Cams sold by CMW and Hitchcocks, without the serious midrange losses that those cams give.
This is your answer to streetable cams for the Bullet that are better than stock, but not as "lumpy" as the Performance Cams or Race Cams.
What we are doing here is re-phasing the stock cams to move the intake valve closing timing of the intake cam later in the cycle, where we can use it for better power, while moving the opening timing of the intake valve later, because our  overlap performance is poor enough that it isn't doing us much good at all. We can sacrifice early opening to get later closing, and that effectively extends our useful duration by 14.5 degrees where it will do us some good. We don't really lose anything by opening the intake valve 14.5 degrees later. In fact we gain something in power, and the reduced overlap makes it so we don't lose our bottom end torque. The earlier closing timing on the exhaust also helps reduce overlap, and helps keep bottom end torque. Since we are not revving up real high, the shortened overlap period is not hurting us.
It's the answer to hot road cams for the Bullet.

Now, you mentioned roller cams. Well, we really can't design and have these roller cams made for any affordable sum. But we can get some of their effects in another way.
This is pretty complex, and I hope I'm not losing anybody.
The hemi head in the Bullet is very good at low lift breathing capability. The hemi chamber is not shrouded by chamber walls like bathtub chambers are. This is a big breathing advantage over most chamber types. And we have low lift cams, and an engine design which mechanically limits us from getting into the hi-lift neighborhood.
So, we can try to maximize the low-lift flow performance of our system, to get more air in there in the low-lift area that we can access.
If you look at the valve and valve seat, they use a 45 degree seat angle, like most engines do. The valve needs to lift off the seat at least .040" before the valve is high enough to unshroud the valve curtain and allow relatively unimpeded flow into the cylinder, because the seat angle creates this condition. Normally, in bathtub chamber heads, this is not an issue because the chamber walls are partially shrouding the valve anyway, and the 45 degree seat directs the incoming air up along the chamber wall. But, in a hemi head, we don't have chamber wall shrouding, so we can work with the seat angle.
David Vizard, head porting guru, has done alot of work with Mopar Hemi heads, and has found that they can benefit from shallower seat angles. A hemi is a hemi, so the Bullet can also benefit from shallower seat angles for the same reasons.
If we can't get alot higher lift, we can start our flow earlier and get more out of our low-lift area, where most engine builders just ignore.
By cutting in a 30 degree valve seat angle on the seat and the valve, we can unshroud the valve curtain earlier, and begin flow at lower lift than the 45 degree seat would allow.
In practice, this does the same effect as a roller cam. It has been shown possible to get 15-25% more power out of a hemi head by using a 30 degree seat angle on the intake valve.
Now, with the Bullet, we have to go to the bigger intake valve to get the 30 degree seat angle, and in the process we get more valve area to flow, but we also lose a bit of mixture speed at the valve transition area. However, this would seem to be a good trade, as the benefits can outweigh the losses. We have to be very careful to flow the area around the valve seat to have minimum impedance to the airflow, because we've expanded the area there, and we can't afford to slow the flow any more with bad flow shape. We want to keep as much  flow speed as we can, so we can use that late valve closing timing to best effect.
If we do it right, we can expect about 15-25% greater performance than using a 45 degree valve seat angle.
This could get us into the 35hp neighborhood at the rear wheel, if all goes well.
And it will all run on pump gas.

This stuff is highly critical in nature, to make sure that it all comes together right. There is not alot of room for making mistakes. It's for the experienced builder. But, it provides a way to get good power and torque in the Bullet, without much or any sacrifices, and doesn't cost a huge sum of money, but takes alot of time and care.
Perhaps even if you don't get everything exact, you can still get a good fraction of the performance, and wind up with 30hp or maybe 32hp.

Since we're operating now with higher compression and better breathing, we need to retard the ignition timing to suit. About 30 degrees of max advance would be about right, or maybe even a bit less. Failure to address the ignition timing issues will cost you a burnt piston.

Truthfully, this is about on the ragged edge that a stock bottom end can take, and it could push some "less than perfect" stock bottom ends over the edge, and take out the big end or the main bearings, or even the rod. And the stock clutch won't handle this either.
Best bet would be to use the billet crank and steel rod setup, and the expensive racing  clutch.
With that setup, you'll be able to wind it to 6000rpm without concern of failure, and it will really kick ass for a street Bullet.

Again, this is not for just "throwing together a bunch of parts". This is to be done with the same care as if you were building a racing engine, which ispretty much what you are doing.



« Last Edit: January 05, 2009, 04:13:26 AM by ace.cafe »
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Blltrdr

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Re: Let's talk about cams.
« Reply #13 on: January 05, 2009, 04:30:19 AM »
 Ace, wow-wow-wow! That's some great technical writing and explained in a way that most will grasp.  Will the installation of the adjustable cam spindles and the re-phasing of the cams bring the HP up to Redditch specs on a stock motor or is it in conjunction with the high comp piston? Also, are you planning on installing a set of these spindles yourself? This has been a very entertaining thread, keep up the good work!   Blltrdr
« Last Edit: January 05, 2009, 04:33:09 AM by Blltrdr »
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Re: Let's talk about cams.
« Reply #14 on: January 05, 2009, 05:00:13 AM »
Ace, wow-wow-wow! That's some great technical writing and explained in a way that most will grasp.  Will the installation of the adjustable cam spindles and the re-phasing of the cams bring the HP up to Redditch specs on a stock motor or is it in conjunction with the high comp piston? Also, are you planning on installing a set of these spindles yourself? This has been a very entertaining thread, keep up the good work!   Blltrdr

Blltrdr,
Just to clarify, I'm discussing the adjustable timing PINION, not adjustable cam spindles.
The adjustable timing pinion is a replacement  for the standard crankshaft pinion gear which drives the cams. The adjustable one offers 2 extra keyway slots on it, so that it can provide 4.5 degrees of change in cam timng, either advanced or retarded, depending which keyway you line up on the crank key.

Yes, you absolutely do need to use the higher compression piston to get the benefit from this rephase of cams, when changing by one tooth.
I haven't done this on my road Bullet yet, because I haven't purchased the hi-compression piston for it yet.
But, I know at least 3 people who have done it on their Bullets with fine success, and one is racing with this cam option. It has been proven to work as stated.
I will be re-phasing my cams as soon as I can afford to get the piston necessary to complete the job. Without the hi-compression piston, it's not appropriate to do the cam change.
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Blltrdr

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Re: Let's talk about cams.
« Reply #15 on: January 05, 2009, 05:30:49 AM »
Blltrdr,
Just to clarify, I'm discussing the adjustable timing PINION, not adjustable cam spindles.
The adjustable timing pinion is a replacement  for the standard crankshaft pinion gear which drives the cams. The adjustable one offers 2 extra keyway slots on it, so that it can provide 4.5 degrees of change in cam timng, either advanced or retarded, depending which keyway you line up on the crank key.

Yes, you absolutely do need to use the higher compression piston to get the benefit from this re-phase of cams, when changing by one tooth.
I haven't done this on my road Bullet yet, because I haven't purchased the hi-compression piston for it yet.
But, I know at least 3 people who have done it on their Bullets with fine success, and one is racing with this cam option. It has been proven to work as stated.
I will be re-phasing my cams as soon as I can afford to get the piston necessary to complete the job. Without the hi-compression piston, it's not appropriate to do the cam change.


 Ace, my bad! What is the least amount you would have to raise the compression to re-phase the cams? Also, since I did make mention of adjustable cam spindles; could you please give an explanation of their use. Thanks, Blltrdr
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ace.cafe

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Re: Let's talk about cams.
« Reply #16 on: January 05, 2009, 01:52:31 PM »
Blltrdr,
Just to clarify, I'm discussing the adjustable timing PINION, not adjustable cam spindles.
The adjustable timing pinion is a replacement  for the standard crankshaft pinion gear which drives the cams. The adjustable one offers 2 extra keyway slots on it, so that it can provide 4.5 degrees of change in cam timng, either advanced or retarded, depending which keyway you line up on the crank key.

Yes, you absolutely do need to use the higher compression piston to get the benefit from this re-phase of cams, when changing by one tooth.
I haven't done this on my road Bullet yet, because I haven't purchased the hi-compression piston for it yet.
But, I know at least 3 people who have done it on their Bullets with fine success, and one is racing with this cam option. It has been proven to work as stated.
I will be re-phasing my cams as soon as I can afford to get the piston necessary to complete the job. Without the hi-compression piston, it's not appropriate to do the cam change.


 Ace, my bad! What is the least amount you would have to raise the compression to re-phase the cams? Also, since I did make mention of adjustable cam spindles; could you please give an explanation of their use. Thanks, Blltrdr

I should expect that a minimum of about 7.5:1 compression piston should do it.

The adjustable cam spindles are for adjusting gear lash between the cam gears, primarily to make them run quieter. It can be quite a fiddle to try to change those, because I've heard of people removing their old ones, and the new ones didn't fit.
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Re: Let's talk about cams.
« Reply #17 on: January 05, 2009, 06:51:09 PM »
Thanks for all the great info, Ace.

Sadly, my diesel's cams don't offer any performance mods I know of. I suppose one could make your own cams if you happened to own a really well equipped machine shop...

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Re: Let's talk about cams.
« Reply #18 on: January 07, 2009, 05:45:53 AM »
Thanks Ace! I am following you loud and clear.
 I was wondering now, since we have a Hemi head, what about reverse dome pistons and plug indexing? You know, make as perfect a circle out of the combustion chamber as possible and have the plug exposed to the incoming charge?
 I know we can all do indexing but a one off piston, mirroring the head chamber and flipped around so we get a sort of sphere, what that gonna cost? I know it can be done but then you have issues with maintaining compression etc....

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Re: Let's talk about cams.
« Reply #19 on: January 07, 2009, 05:50:20 AM »
I should clarify. The theoretical advantage of this would be the lessening of tight spaces and sharp edges in the combustion chamber. There by minimizing hot spots that cause detonation. Its been so long since I thought of all this that my mind is reeling trying to remember all the different factors.

ace.cafe

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Re: Let's talk about cams.
« Reply #20 on: January 07, 2009, 02:24:27 PM »
Thanks Ace! I am following you loud and clear.
 I was wondering now, since we have a Hemi head, what about reverse dome pistons and plug indexing? You know, make as perfect a circle out of the combustion chamber as possible and have the plug exposed to the incoming charge?
 I know we can all do indexing but a one off piston, mirroring the head chamber and flipped around so we get a sort of sphere, what that gonna cost? I know it can be done but then you have issues with maintaining compression etc....

Jon,
Plug indexing is a good thing in any engine. In our hemi head, the open side of the plug electrode should aim toward the center, with a slight bias toward the intake valve.

Reverse dome pistons are not possible, without lowering compression dramatically, which is counterproductive. Even our 6.5:1 stock pistons have domes, although rather low domes.
In practice, the dome height is not a severe impediment to flame propagation until it is so high as to nearly divide the chamber in two, at which time it is suitable to twin-plug the chamber with a second spark plug in the decompressor hole.
For street applications, this isn't an issue, since we'll never get a dome that high in a street bike that runs on pump gas.

The dished pistons, or "inverted chambers", come with other head designs that have nearly zero combustion chamber in the head, and the valves sit flat on the head surface, or with a minimum of shaping around them. The combustion chamber shape is then milled into the crown of the piston. This was popular with the Jaguar V12 engines, in the "HE" versions which used the "Fireball head", with a combustion layout like that. I'm sure other engines have used this design, but I don't know which other ones.

There are all kinds of things that can be done when you have a blank sheet of paper.
But, in the case of modifications, we have most of the parameters already existing, so we have an envelope to work inside, and we do what we can with it.
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Re: Let's talk about cams.
« Reply #21 on: January 07, 2009, 04:01:15 PM »
Holy shit.  One day I might be able to follow all this awesome knowledge!   :-[
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Re: Let's talk about cams.
« Reply #22 on: January 11, 2009, 02:51:57 AM »
I have been enjoying your tech threads Ace. I have to admit much of it is over my head, but as a former racer, I get the general gist. It sounds to me like you would be the guy to design an AVL performance kit encompassing head/valve work, and new cam design.

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Re: Let's talk about cams.
« Reply #23 on: January 11, 2009, 05:43:09 AM »
I have been enjoying your tech threads Ace. I have to admit much of it is over my head, but as a former racer, I get the general gist. It sounds to me like you would be the guy to design an AVL performance kit encompassing head/valve work, and new cam design.

I'd welcome an opportunity to do that with the AVL.
I've focused primarily on the old Bullet engine, because that is what I have, and what has been modified most, and there is some tested data to go on.
I've seen some photos of the AVL head, which were mailed to me from one of the members on the Hitchcock forum. It appears to have even larger ports than the old Bullet engine, so there are some challenges there. I think it would be an interesting project.

I'm also looking forward to getting some more exposure to the new UCE engine, so that I may be able to develop some ideas for that too.
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jonapplegate

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Re: Let's talk about cams.
« Reply #24 on: January 12, 2009, 03:41:47 AM »
I have never seen the inside of our head. I am not talking about that old style of combustion chamber like I believe the Chevy 409 had where the combustion chamber is part of the piston. I actually cant remember if that is correct. Like I have said, it has been a long time. We are probably talking the same thing and I am not understanding. When I say reverse dome I mean a piston that has been designed with a mirror image, rotated 180 degrees, of the cylinder head combustion chamber. The piston is tall enough so as to create a sort of Hemispherical chamber. Very little "flat" surface left around the  head and piston. Just enough so there is no contact. I know it can be done with conventional V8 engines. I have seen it. Since this would effectively create a smaller combustion chamber (as well as a taller piston, might you actually have to have a deeper depression in the piston?
  All this is theoretical in regards to our Bullets since there is probably very little options available out there for our needs.
  Arias(?) pistons are what I seem to remember being used. Perhaps pistons intended for boosted engines?  No, that isn't correct. Boosted engines would be lower        compression ratio. This engine, Mopar 340 or 360, was spec'ed to be 9.5 to 1. Later boosted to 10.5 to 1 to make up for heat loss due to aluminium heads being added. I think the heads had smaller combustion chambers cast. Or it was shaved.
 Anyhow, if one had the money and desire, I think it could be done. This little trick was believed to go along way towards improving efficiency although I remember that there was some serious flogging time required to get the timing right.
 My friend Rick was a serious engine builder who had time, and money, on his side. I used to stand around and chew the fat with this guy all the time. He actually didn't know that much about internal combustion engines I don't think. He just heard of an idea that sounded to have promise and then began calling around.
 Wouldn't it be nice?
 All I can say is Rick had the hardest running small block vehicle (Dodge Dart) I had ever had the pleasure to drive. All the while remaining streetable. I had a small block Ford for a while that although was a beast it was so high strung I couldn't run it on pump gas without adding octane boost and it always had something not right. I quickly tired of it.
 So, I am looking forward to your reply about the piston.

 Now, what about a shorter piston and longer rod so we can increase the rod to stroke ratio? This can also dramatically increase efficiency but also is a bit advanced. Obviously couldn't be done in conjunction with a reverse dome. Not enough piston.
 Does anyone know what the rod to stroke ratio is? I would figure it out myself but I have no idea what the rod length is.   

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Re: Let's talk about cams.
« Reply #25 on: January 12, 2009, 02:38:02 PM »
Jon, I'd have to see more specifics about this piston design you're describing.
From what I'm hearing, there'd have to be alot more to the whole thing than I'm getting in the description, and would certainly require an entire new head design, or else the compression would be so low that the engine wouldn't even run. You can't double the effective combustion chamber volume and not expect compression to drop thru the floor. Where are you going to pick up that lost compression?
A flat top piston or mild dome is not hindering flame travel, or burn, and is just fine from a combustion efficiency point of view.

I'm open to hearing more, of course. However, consider me skeptical about it at this point.

A shorter piston on the Bullet would certainly be a place for improvement. Not because we could lengthen the rod, but just because the Bullet has a very low placement of the gudgeon pin when compared with most other engines. This causes some less desirable piston action in terms of rocking. That could be an improvement, and we could shorten the barrel commensurately, and get the results, IF somebody would be kind enough to make a batch of pistons to suit. So far, we can barely even get a decent piston, much less a "perfected one" that requires engine mods to suit it. There are no "really great" pistons available for the Bullet from anybody. There are a couple of "good" ones, and a bunch of "crappy" ones, but no "perfected" ones.

As for rod/stroke ratios, the Bullet is already a long rod motor, with a ratio of nearly 2:1 rod/stroke. There are good points and bad points that come along with that.
For a shorter rod version, you only have to look as far as the Electra X AVL engine for that. The rod in the AVL is shortened along with the barrel, to make room for the taller cylinder head that the AVL uses.
« Last Edit: January 12, 2009, 02:50:38 PM by ace.cafe »
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jonapplegate

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Re: Let's talk about cams.
« Reply #26 on: January 17, 2009, 03:32:15 AM »
If the Rod/ Stroke is already 2 to 1 I doubt that there is any reason to investigate that option further as I seem to remember that this is what builders where shooting for and anything more than that would almost require a taller deck. The idea was that a "longer rod, shorter piston" would "park" the piston at near TDC for a bit longer time thereby increasing efficiency by letting the air/fuel mix burn longer at max compression.
  About the reverse dome design. Perhaps the piston was not a true mirror image but simply a sort of modified dish that somewhat replicated the shape of the head. tis possible that the piston dish was not nearly as deep as the head. I neglected to say that these heads would have been very Hi-Po heads with a very small cc combustion chamber in the first place. It's been twenty five years since I saw this and it may even have been proven to be useless since.
However, the more I envision this in my mind I cant see why this wouldn't equal a better combustion chamber. You would end up with something much closer to at least an oval combustion chamber. Or like I have mentioned, one free from many of the "hot spots" that can create pre-ignition.
  Enjoying this chat about combustion and increasing efficiency even if it is all for naught.

ace.cafe

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Re: Let's talk about cams.
« Reply #27 on: January 17, 2009, 03:22:17 PM »
Jon,
As I mentioned previously, a piston type you refer to has been used, but primarly in engines with very little combustion chamber volume iin the head itself, such as the Jaguar V12 HE "Fireball head". It essentially reverses the position of the combustion chamber shape into the piston crown, instead of in the head.
In practice, a hemi does basically what I think you are intending to achieve, but does it in a "half-sphere" which is what a hemi-chamber is.
And, it suffers from the conditions which are present in a hemi-chamber, and which also would cause issues with hi-compression in the "sphere" design you describe, because of the lack of "squish/quench" area, which results in detonation at high compressions. In fact, one of the main reasons why our engine is compression-limited is because there's no quench area in the chamber, so anything higher than about 8.5:1 compression results in detonation from lack of chamber swirl, unless fuel modifcations are present, such as octane boosters or the like. Whereas, if we had a piston that offered good quench area, we could probably run 10.5:1 on hi-test pump gas without detonation. But, nobody is making such a piston for us, so that's that.

Regarding the long rod, it's a geometrical issue involving thrust angles. And it does affect dwell time as well as MBT angle, and affects the overall stroke behavior in all strokes, including changing the flow curves for breathng. And a long rod weighs more.

In the case of the Bullet, we have a long stroke and a long rod and a long piston.
It's LOOOOOOOOOONG  in all kinds of ways.

I think it's great that you're interested in this stuff.
I'd recommend doing some basic research into the most basic and even boring aspects of engine design theory, so that you start with a full understanding of what things do, and how they can be manipulated for different results.
The "golden rule" of modding is  "Just because it worked in different application, does not necessarily mean it's going to work in my application". So always look at everything in total, and how it all works together, and crunch the numbers to see what's what in YOUR application. Some of the most basic and earliest design decisions that you make, can actually "cast in concrete" how much power your engine will eventually be able to produce.

An excellent example of this could be made with some of the stuff I wrote on this thread.
Let's say that you heard from Harry Hot Shoe, who races NHRA dragsters, that huge ports are the best way to make power, and open them up as big as you can for better breathing. So, you grind open the Bulet ports to 34mm or even bigger, and use a 1.5" Amal GP carb to feed huge air volumes in.
Then you read my thread here on late iintake valve closing timing, and think "Hey! That's the ticket! I want that too!" And so then you re-phase your cams, and the engine doesn't respond as expected, and in fact gets worse.
Well, big slow ports and late IVC timing are not terribly compatible, and they work against each other in most applications, so you pick which approach you are going to go for YOUR application. You don't necessarily try to "get both", because "both" may not work..
So, virtually nothing actually "stands alone" in an engine design. It all depends on the way the rest of the engine is designed and working, to make any mod work properly.
There's alot of engines out there that have been modded poorly, and are actually worse than stock.
« Last Edit: January 17, 2009, 03:53:47 PM by ace.cafe »
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Re: Let's talk about cams.
« Reply #28 on: January 17, 2009, 05:02:45 PM »
     Most of the modified engines that come through my shop are as Ace said, not as good as stock. Often they run poorly in most RPM bands except perhaps one. When they finally hit  the RPM where every thing works they seem to come alive. The rider thinks it's great because there is more power. In reality there is not much more, it just seems like it because the contrast is much more marked than before.
     If the engine had been left alone it would have much more usable power over a much greater range of use. You really have to take a whole engine and use approach to modifications to get what you are looking for.

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Re: Let's talk about cams.
« Reply #29 on: January 18, 2009, 07:16:01 AM »
This is excellent information, but it seems pretty well targeted to race engine development.  I have to side with Vince...a stock engine is probably better in most ways for the street.  I'd love to see the dyno curves for these cam & flow mods.

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Re: Let's talk about cams.
« Reply #30 on: January 18, 2009, 08:42:22 AM »
I agree with everything Ace, and Vince, said and I believe I am just not communicating quite clearly. I know just enough to be dangerous but not enough to truly run with you "big dogs". I mean that as a compliment to you. Most of my limited knowledge is 90 degree V8 centered and I know that head design dictates piston design parameters. RE doesn't need longer rods, they are already as long as practical from your mention of 2 to 1 rod/stroke ratio. Search "reverse dome" and you will see that many piston makers still produce these pistons, for I believe readily available heads, at fairly high comp. ratios. Its winter and I am dreaming about engine building so most of this is "theoretically, what can we do with OUR powerplants.' I don't ever expect to actually be able to do any of these things. I also have learned, with your help, that watercooled multi-cyl "V" engines occupy an entirely different universe than do air-cooled singles so much of my "knowledge, such that it may be" doesn't really tranlate to the RE.
 Re-reading my post, I hope that I am not coming across as cranky, I am most certainly not. I greatly enjoy learning from you all.
 I am also 100% in agreement that "built" engines generaly do not behave very well compared to a stock engine. It takes a very light touch and well thought out approach to build a more powerful engine that doesn't favor a very narrow performance window. Thats why I like the  "little bit here, little bit there" approach now, concentrating on mid range. Boring to most, I believe this is where you get  the most return on streetable machines. Go for low end torque, good luck getting traction. Go for high rpm, hope you like low gears and/or crappy street driving.

ace.cafe

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Re: Let's talk about cams.
« Reply #31 on: January 18, 2009, 02:26:39 PM »
Yes Jon, I agree that street-ability is very important for a road bike.

Most of the stuff that I've been discussing on this thread is actually targeted at the street Bullet performance.
It's possible to get much higher levels of power out of a racing Bullet engine, but as you mention, it's not desirable for street use when you hot-rod it up that far.

The typical max parameters for the Bullet to work well for street riding are 30hp/30ft.lbs and about 8:1-8.5:1 compression, and no more than 5500 rpm with the stock bottom end.
And that's what I've described in most of my discussions on this thread.
If you do the right head work and carb and exhaust, and then include the hi-comp piston and re-phase the cams(if your particular cams will allow it), and retard the ignition about 4 degrees or so,  then you can get into the 30hp neighborhood, if you did everything real well. Maybe a bit less, but it can get into that neighborhood. And, this is rear-wheel power, so you can add ~15%-20% to that for crankshaft power. Maybe around 35hp at the crank.
I understand that the Bullet's torque curve is the main attraction, and it's silly to compromise that for a few extra hp on the top end which will not often be used. So, my recommended mods on this thread are aimed at retaining the same general riding characteristics of the Bullet, but giving some more power too, with the same sort of nice wide torque band that the Bullet has.

These mods will add stress to the stock bottom end, though. So, it may not last as long as a plain stock Bullet. And that is sort of to be expected when increasing power to double the stock power, such as we're talking about. If you want the added longevity and peace of mind, it's a good idea to purchase the European Performance Crank with forged steel rod and oversize Alpha roller bearing, and some good quality European or Japanese made main bearings.
That will beef up the bottom end enough so that you won't have any concerns about bottom-end strength. And you'll need a stronger clutch to hold the power, The stock clutch will slip. It can't hold that power level.
That' crankshaft assembly is the most expensive part in the mix, and it's not totally mandatory to have it, but it is advisable if you can afford it. The stock con-rod is often pretty marginal, and could give up at higher rpms, throw it thru the crankcase, and making an expensive junk pile out of the engine. And that's not uncommon. So, if you can afford the good crank, then get it, and rest easier.
« Last Edit: January 18, 2009, 02:37:45 PM by ace.cafe »
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Re: Let's talk about cams.
« Reply #32 on: January 18, 2009, 02:57:57 PM »
This is excellent information, but it seems pretty well targeted to race engine development.  I have to side with Vince...a stock engine is probably better in most ways for the street.  I'd love to see the dyno curves for these cam & flow mods.

Earl,
I don't have the dyno curves for them. They were done by some other guys that I've consulted with in our Bullet Performance Group. The flow work was modeled on a computer program made by one of the famous flow-bench makers, and is used to determine what theoretically will happen when you do things to ports and valves. One of the guys working on this was a port-man at Yoshimura.
Alan Hitchcock also did some work on this, and got similar figures on his dyno, but they weren't published.

However, I can tell you that the re-phased cams, when used with the hi-compression piston, will give power within 1hp of the "Performance Cam" set from Hitchcocks and the same hi-comp piston, and do it at a lower peak rpm which the stock bottom end can reach fairly safely, and does not lose midrange torque(which is a problem with the Performance Cams). We felt that giving up that 1 hp at the top end, was worth the trade to get back the midrange losses that Alan gave up by widening the overlap for top-end power. We think this is a better street performance setup, while we do acknowledge that it does have 1 less hp at the top.
The key to this is that the re-phase shifts the duration band of the intake cam retarded for later intake valve closing timing, but the resulting retard of the intake opening timing doesn't hurt us because our engine isn't good at utilizing the overlap period, so reducing overlap actually assists cylinder trap, and we win all the way around.

This late intake opening gives us more power at the higher end of the rpm band, and the reduced overlap period gives us better cylinder trap to keep our torque up in the low and midrange rpms. Good fast port flow and compression above 8:1 are necessary for this to work right. And it is preferred to use a degree wheel and dial indicator for this.

Any of this stuff could be considered to be "racing mods", but I focused on "mild racing mods" which could conceivably still be used with the stock bottom-end, albeit with some unknown level of possible reduced longevity or reliability, depending on how good the bottom-end in the particular engine being modded happens to be. And they do vary. A suspect bottom-end might not last too long after being modded like that.
« Last Edit: January 18, 2009, 03:07:52 PM by ace.cafe »
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Re: Let's talk about cams.
« Reply #33 on: January 18, 2009, 04:14:24 PM »
 Ace, love this thread! I think your thought on re-phasing the cams and using a 7.5:1 piston to develop about 25 HP is right in the ballpark. Now would this be HP measured at the rear wheel? This would be very streetable/reliable mod. Would you use aluminum barrel/piston set-up or standard? This would really be a vast improvement from stock considering the true HP to be under 22. All we need now is a technical note to explain the proper procedures to go about this in the right manner!   Blltrdr
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Re: Let's talk about cams.
« Reply #34 on: January 18, 2009, 04:58:51 PM »
I just want to thank y'all for all of this great information regarding Bullet engine mods.I am so glad I did not jump in with zero knowledge,as usual,before I found this site.I  have some mild sorting out to do just with the exhaust,carb enrichment.I am gonna do one small thing at a time,get that right before going ahead.I,too,have previous experience with mostly automobile engines,modifying them for basically the drag strip.Have actually found that wieght reduction is most productive coupled with gear reduction.Don't really apply here,much.I do not see a big potential here,anyway.But I am a hot rodder at heart and want all I can get that is reasonable.If one does the degree wheel check of the cam timing and finds that rephasing is out where do you go from there,is that very common?All the cam manufacturers say to do this and I've never seen a camshaft that was off.The shop I used to use never had either.They only dealt with the big 3 auto engines,circle track.I am really fascinated with this cam rephase,no doubt will do it but not till next winter.

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Re: Let's talk about cams.
« Reply #35 on: January 18, 2009, 05:03:29 PM »
Ace, love this thread! I think your thought on re-phasing the cams and using a 7.5:1 piston to develop about 25 HP is right in the ballpark. Now would this be HP measured at the rear wheel? This would be very streetable/reliable mod. Would you use aluminum barrel/piston set-up or standard? This would really be a vast improvement from stock considering the true HP to be under 22. All we need now is a technical note to explain the proper procedures to go about this in the right manner!   Blltrdr

Yes, that would be an "estimate" of hp at the rear-wheel, because there was no actual testing with 7.5:1 compression. They tested with 8.5:1, which gave higher power figures at the rear wheel in actual testing. But, the 7.5:1 would be okay to use for the application, with less overall power being the result. But, it's easier on the bottom-end of the engine with that lower compression. I wouldn't go any lower than the 7.5:1, because we do need some compression boost to overcome the inital compression-building losses that occur at the beginning of the compression stroke with late intake valve closing timing. This is the case with nearly any performance cam setup. They all need some boost in compression to work right.

Stock "true" hp at the rear wheel is usually about 16hp with the 5-speed gearbox, and  about 14-15 hp with the 4-speed gearbox, which uses grease inside and uses up some more power in transmission losses.
So yes, it is a significant imporvement over stock.
If you have the bigger carb and the free-flow intake and exhaust system, you have about 20-22 hp at the rear wheel then. Maybe even 23, depending on how well it's all working. The added compression is good for 2-3 hp, and the cams are good for about 3 hp on top of what you get with the piston. So yeah, with the 8.5 you'd get near to 30hp, and with 7.5 you'd get maybe 26 or so at the rear wheel, which is a full 10hp more than stock, or about 62% power increase over stock. The setup with 8.5:1 would be close to 75% power increase over stock. And if you did some good porting and throating work, and a real good tuning job, you could get close to 100% power increase over stock, with a setup like this. Maybe not quite, but close.
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Re: Let's talk about cams.
« Reply #36 on: January 18, 2009, 05:21:34 PM »
 Now how about that tech note for re-phasing the cams, Ace? Is that something you would be willing to do? I think there would be plenty of interest in this. Blltrdr
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Re: Let's talk about cams.
« Reply #37 on: January 18, 2009, 05:25:35 PM »
I just want to thank y'all for all of this great information regarding Bullet engine mods.I am so glad I did not jump in with zero knowledge,as usual,before I found this site.I  have some mild sorting out to do just with the exhaust,carb enrichment.I am gonna do one small thing at a time,get that right before going ahead.I,too,have previous experience with mostly automobile engines,modifying them for basically the drag strip.Have actually found that wieght reduction is most productive coupled with gear reduction.Don't really apply here,much.I do not see a big potential here,anyway.But I am a hot rodder at heart and want all I can get that is reasonable.If one does the degree wheel check of the cam timing and finds that rephasing is out where do you go from there,is that very common?All the cam manufacturers say to do this and I've never seen a camshaft that was off.The shop I used to use never had either.They only dealt with the big 3 auto engines,circle track.I am really fascinated with this cam rephase,no doubt will do it but not till next winter.

Bullet cams do vary in tming from one to the next.
I think it is somewhat due to accepting wider variance in part manufacture than we see at other companies. But part of it may have been some intentional changes that they were trying with cam timings. There have been 10% differences in timing noted from different cams over the last 10 years of production, and we don't know exactly what the reason is, but we know it has been seen.
So, that's why we need to check what we've got in our particular engine before we go ahead and start changing stuff.
Basically, if your intake cam shows a closing timing of anything after 65 degrees ABDC with a .012" lash setting for test purposes, then you are not a candidate for this type of rephasing, unless you get another cam set that would work with the re-phase.
Preferably, you should have an intake closing timing of 60 degrees ABDC at .012" lash, which is the factory spec. Then if you retard the intake one tooth, and then use the adjustable timing pinion to advance the intake and exaust cams together as a pair, you would wind up with an intake closing time of 73.5 degrees ABDC at .012" lash, for an intake closing timing, which is exactly what we want.
If your actual measured timing is within a few degrees of this, it will be okay. If your re-phased timing is showing closing time later than 75 degrees ABDC at .012" lash, then it's a little late and will bias your power even higher on the powerband and sacrifice some of the lower end power because of increased compression-building losses, and if you exceed 80 degrees ABDC, it's not really useable for this mod. Then you'd have to try a different set of cams that timed in their stock positions closer to the 60 degrees ABDC spec that they are supposed to be, as your starting point for re-phasing.
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Re: Let's talk about cams.
« Reply #38 on: January 18, 2009, 05:31:44 PM »
Now how about that tech note for re-phasing the cams, Ace? Is that something you would be willing to do? I think there would be plenty of interest in this. Blltrdr

Yes', I'll do this as soon as I can get around to it.
It's a big writing job, and I have to be real careful how I word it, so that we don't have half the people on the forum fucking up their engines because I didn't make something exactly clear.
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Re: Let's talk about cams.
« Reply #39 on: January 18, 2009, 05:45:03 PM »
Yes', I'll do this as soon as I can get around to it.
It's a big writing job, and I have to be real careful how I word it, so that we don't have half the people on the forum fucking up their engines because I didn't make something exactly clear.

 Well put! You would definitely have the power to single handedly screw up most Bullet motors with a few misguided key strokes. If you don't suffer from MPD I think we will be in good hands.  Blltrdr
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Re: Let's talk about cams.
« Reply #40 on: January 18, 2009, 06:05:30 PM »
Love the tech threads. When I used to race small cars in Japan, some of the other  Americans still had the old muscle car mentality, always looking for the one big fix. They would look for max displacement, ignoring engine characteristics. They would stiffen springs without using better shocks (wheel hop). It was entertaining.

I always looked for a wide vaiety of small changes that worked together. I may have never achieved the peak numbers that some did, but usable power/torque on the road, throughout the rpm range, usually brought home the trophys.

I think that the RE will always be a slow reving/low reving motor. Even with lots of power, I don't think it would be much faster. So, why not forget about speed and acceleration, and look for improvements that enhance the characteristics we buy them for: broad power range, ample torque, visceral feel.

I think Ace, Vince and some others have the knowlege to create or at least design the kinds of performance kits that we would ll really love. We will never beat the kid on the sport bike to the next stop light, but he will still envy the smile on our faces.

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Re: Let's talk about cams.
« Reply #41 on: January 18, 2009, 06:18:36 PM »

I think Ace, Vince and some others have the knowlege to create or at least design the kinds of performance kits that we would ll really love. We will never beat the kid on the sport bike to the next stop light, but he will still envy the smile on our faces.

Actually, the info on this thread, and the other ones about head porting and engine modifications, are the performance kit that you refer to.

The difference with this "kit" is that you don't have to buy it. Or, at least you don't have to buy much.
You just have to know what to do.

A piston and a retarding of the ignition timing to suit, some basic head work, the adjustable timing pinion for the cam re-phase, and the usual filter, carb, exhaust mods,  and a "beefed-up" clutch, and you have a very streetable Bullet that will go real good and doesn't cost an arm and a leg.

And, if anyone doesn't have the capacity to do these things, but would like them done, just contact me, and we can make arrangements to ship your engine, or your head, or whatever you need done, to me, and I'll do them and ship them back to you.
I'll do it on a time and materials cost basis.
Performance work only, please. I don't intend to distract people from the dealer network for repairs, nor would I even want to do that.
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Re: Let's talk about cams.
« Reply #42 on: January 18, 2009, 06:25:29 PM »
Ace,

let me guess you live in the US?!

Cheers, Johann

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Re: Let's talk about cams.
« Reply #43 on: January 18, 2009, 07:10:17 PM »
Just a little off topic.

How's about a four valve head pushrod driven designed by Dr. McGuigan in the mid '90s at the Royal Military College of Science.
Originally designed for the diesel project bike he designed on the basis of a 500 Bullet engine with beefed-up crank. Maybe this head could be used for a petrol engine with only minor modifications.
...if Dr. Stuart McGuigan would be so kind and be allowed to hand over this design work to just Bullet enthusiasts.




Regards, Johann



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Re: Let's talk about cams.
« Reply #44 on: January 18, 2009, 09:21:07 PM »
Johann,

Pretty cool diagram you dug up there!
That engine is apparently one of the designs which contributed to the AVL engine we have today.
Notice the head has the AVL-style rocker system and cover plates.

I'm sure that the 4-valve design, while very attractive, was deleted because of the rev-limited nature of the long-stroke Bullet, which really can't rev high enough to get value from the lighter valve mass that the 4-valve system offers.
In the sub-6k rpm ranges we run in, the 4-valve design only adds complexity and expense, because the 2-valve system can be easily controlled at those rpms, and doesn't need the lighter valve masses which the 4-valve system provides until much higher rpm speeds that we don't reach with the Bullet engine. And the 2-valve system already provides plenty of valve area as it is in standard Bullet configuration.
So, while it's "cool" and everything, I don't see any real advantages to it for the street engine, but it might be nice for a high-revving racer.

You don't happen to have one of those heads "laying around in your closet", do you? I'd sure like to see one of those things up close.
« Last Edit: January 18, 2009, 09:26:58 PM by ace.cafe »
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Re: Let's talk about cams.
« Reply #45 on: January 18, 2009, 09:58:12 PM »

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Re: Let's talk about cams.
« Reply #46 on: January 18, 2009, 10:03:54 PM »
Ace,

this design was used on the '95 diesel demonstrator engine which had 547cc and produced between 16-18 BHP.
I've never been close to one and will never be.
If you're interested to talk to Dr. McGuigan: [email protected]

Regards, Johann




Very interesting!
Geoff should see this!

However, I must admit that I am at a loss to explain why they decided to put 4 valves into that.
I guess Dr. McGuigan is smarter than I am, which really comes as no surprise to me!
« Last Edit: January 18, 2009, 10:14:48 PM by ace.cafe »
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Re: Let's talk about cams.
« Reply #47 on: January 19, 2009, 05:46:01 AM »
... I can tell you that the re-phased cams, when used with the hi-compression piston, will give power within 1hp of the "Performance Cam" set from Hitchcocks and the same hi-comp piston, and do it at a lower peak rpm which the stock bottom end can reach fairly safely, and does not lose midrange torque(which is a problem with the Performance Cams).

That's what I'm talking about!  This makes more sense to me.  I would always figure in some bottom-end improvements for almost any high-power mods, but this sounds like a  sensible improvement for the money invested.  All power increases have to be targeted at the end use...my old man used to wrench for a stock car team, and was able to make a slant-six Dodge beat the bigger Chevys just by getting the power band to match the needs of the track, and then training the driver.  Thanks for getting together a real-world package of ideas.

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Re: Let's talk about cams.
« Reply #48 on: January 19, 2009, 04:48:58 PM »
I wish someone would sell phased cams for the RE. I don't have the skills to machine a set for myself.

Whenever my X needs a ring job, I may put in the new 535 piston and shave the head for 9:1 comp. With phased cams, I would probably have the mid-range grunt of a John Deere tractor. Now that would be fun.

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Re: Let's talk about cams.
« Reply #49 on: January 19, 2009, 06:57:09 PM »
I wish someone would sell phased cams for the RE. I don't have the skills to machine a set for myself.

Whenever my X needs a ring job, I may put in the new 535 piston and shave the head for 9:1 comp. With phased cams, I would probably have the mid-range grunt of a John Deere tractor. Now that would be fun.

Luoma,
All this cam talk I've been doing is directed at the old Iron-Barrel Bullet.
I have never even clocked the cams on an AVL engine, and have no idea how they are timed.
Someone told me that they are "milder" cams than the Iron-Barrel Bullet cams, but I have no idea what their timing is.
So, I cannot say if the re-phasing would, or could, be appropriate, or even be done on that engine.

So, all this stuff must be considered as a potential possiblity for Iron-Barrel Bullet owners only. Not the AVL.
No research that I'm aware of has been done for re-phasing AVL cams.
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Re: Let's talk about cams.
« Reply #50 on: January 22, 2009, 05:59:23 PM »
Wow, ACE - WE ought to bind that in leather and put it on motel nightstands!! VERY well put. As an "old school" tuner, I have (as you obviously have as well ...) learned to maximise a minimum design to stun and amaze the "chrome plated noisy bike crowd" I've done the BSA and Triumph thing for a while - as well as the Norton's and what ever ELSE British rolled down the pipe into the garage. I've followed Enfield for a few years (I had an Interceptor as a "child" ...) and have been wanting to explore the "go fast" on one at a serious level. I see that I have to do nothing but read your posts!! Hahaha!! Keep up the gREat work!
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Re: Let's talk about cams.
« Reply #51 on: January 22, 2009, 06:11:12 PM »
Wow, ACE - WE ought to bind that in leather and put it on motel nightstands!! VERY well put. As an "old school" tuner, I have (as you obviously have as well ...) learned to maximise a minimum design to stun and amaze the "chrome plated noisy bike crowd" I've done the BSA and Triumph thing for a while - as well as the Norton's and what ever ELSE British rolled down the pipe into the garage. I've followed Enfield for a few years (I had an Interceptor as a "child" ...) and have been wanting to explore the "go fast" on one at a serious level. I see that I have to do nothing but read your posts!! Hahaha!! Keep up the gREat work!

Thanks Bob!

If you want to get serious with the Bullet, the first thing you should get is the Hitchcock's Steel Billet Crankshaft with the forged steel con-rod, oversize crankpin and Alpha roller bearing. It all comes pre-assmbled and ready to run, and you can get it from CMW.
Also get the highest quality main bearings you can find that are Europe or Japan, or even the US if you can find any.

Then you have your bottom end sturdy enough to handle whatever you plan to throw at it.
The lower-end on the Bullet is the weak point Con-rods snap, cranks are often out of true, or out of spec in dimension, pistons are crap, and piston speeds get very high when doing any revving.
So, bottom end is the first to do, and then work the power production stuff after that.
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Re: Let's talk about cams.
« Reply #52 on: January 22, 2009, 09:42:28 PM »
ACE - Been there - seen ALL that ....... got the "jay-oh-bee" at Classic Motorworks ... hahaha!!! I just now have HAD a little time to explore the forum after MUCH chiding by the co-workers. I hope to develop a very decent alloy "replacement" rod for the iron barrel fiends (like me) out there as well as a few "voodoo" parts for the regular guy to enjoy. The alloy rod is one of my "god child" projects because the stock one is barely capable of putting up with my old Paw-Paw ass - but the Carillo is a bit spendy for the "regular" guy. My "replacement" one should fill the gap without emptying the wallet.Stay tuned on THAT account ... At least here, I'll have the pick of the broken crap that comes in the door to build a "muley" with .... They'll be happy to get SOME of that stuff out from under the workbenches and "re-stored" somewhere else!! Hahahaha!! I'll keep an eye on your posts! ;)
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Re: Let's talk about cams.
« Reply #53 on: January 22, 2009, 10:43:32 PM »
Hey, that's great, Bob!
Didn't know you were working with CMW.
Congrats!

The alloy rod project sounds interesting. You sure have your work cut out for you with that one.

Let me know if I can help with anything!
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ScooterBob

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Re: Let's talk about cams.
« Reply #54 on: January 23, 2009, 03:50:54 PM »
ACE - I'll sure keep you on the "up front" with the projects .... I'm betting that talking to someoen who HAS scattered one or two of these will save a man a little time .... and some disappointment!! Hahahaha!!
Spare the pig iron - spoil the part!

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Re: Let's talk about cams.
« Reply #55 on: March 08, 2009, 06:01:10 AM »
sorry to be chiming in to such an old series of posts but couldn't help myself. The four valve design probably came out of that time period not so long ago when everyone was thinking of multivalve as a way to increase efficiency and therefore, performance. Two small valves will carry more flow than a similiar sized big valve because of greater vacuum if I recall. Just writing this makes me wonder if that is actually true in practical applications. Even if it is, time showed that in a fairly simple design four valve technology just meant twice the number of things that could go wrong. Also, more parasitic power loss since you have that many more parts siphoning power away from the rear wheels.
 All the very most hipo designs run multi valves but they are designs which every component of the engine is meant to complement the other.
 Okay, I think I think i have gotten that out of my system!

ace.cafe

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Re: Let's talk about cams.
« Reply #56 on: March 08, 2009, 01:37:13 PM »
Jon,
There are pros and cons to any design, no matter what it is.
The multi-valve systems do very well, and they have alot going for them.

We can get a very good result from our little hemi.
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Re: Let's talk about cams.
« Reply #57 on: March 11, 2009, 05:38:25 PM »
Some late breaking results just in.

A member here, "longstrokeclassic" is also a member of a forum in the UK, which I also participate in.
And he decided to do the cam rephase on his 350. I worked with him by internet on the proper instructions, and he did it, along with some other mods.

At first, he had too much power for his clutch to handle, but he upgraded it, and rectified that issue. And he did a bit of running-in for the engine, and then reported. Then when he finished the clutch work, he put the cams back to normal alignment, and ran it to see what the difference was between the 2 different cam timings.

Here is his latest report, which I lifted from his post on the UK forum;
"Whilst fitting the uprated clutch I took the opportunity to swap the inlet cam back so all the timing marks correspond, but left the 3 way pinion insitu running in the advanced position. What this revealed was what I mistakenly thought to be a carburation problem was a soft spot in power delivery at low revs. This disappeared when reverting back to normal cam timing but was also accompanied by a noticable loss of power at the same time.

Without the aid of a dyno I can only hazard a guess at what was happening.
But this is what I think.... With the rephased cams there was a noticable drop in power at low revs but I dont think this was so much a loss in power over the standard setup, but the rephasing providing a sudden increase which made everything below it seem flat in comparison.
Nothing like the sudden power delivery of a two stroke twin or triple coming on song but more like the difference between riding the along flat and then going down a steep hill.

I intend to run the bike with the rephased timing (with the inlet running retarded) because although this provides something of a slight jeckyll & hyde power delivery it does mean I can still potter around at 45-50 without really noticing any difference or can open the bike up and take advantage of the extra acceleration and increase in top speed over the standard when the mood takes or the need arises.

Quite a successful outcome -"
--------------------------------------------------------

So, we see that he got exactly what was expected. He kept approximately the same power as a stock Bullet in the lower revs, and got a significant boost in the upper rpms.
Still very roadworthy and manageable, and spirited when he wants to run hard.

So now we know it works fine on 500, 535, and 350.
I'm still awaiting the report from the 612 user, to see how he liked it.
« Last Edit: March 11, 2009, 05:42:41 PM by ace.cafe »
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Re: Let's talk about cams.
« Reply #58 on: March 11, 2009, 05:46:13 PM »
Ace,

this design was used on the '95 diesel demonstrator engine which had 547cc and produced between 16-18 BHP.
I've never been close to one and will never be.
If you're interested to talk to Dr. McGuigan: [email protected]

Regards, Johann




An Enfield prototype diesel twin? How very cool!

Too bad they didn't go ahead and make it....

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Re: Let's talk about cams.
« Reply #59 on: March 11, 2009, 05:54:13 PM »
 I suspect all the data collected will be used in the development of your new cams. I would figure the new cam design will eliminate any need for the 3-way pinion or the re-phasing. This thread keeps getting better. Keep it coming Ace, It's almost lunchtime!  :P

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Re: Let's talk about cams.
« Reply #60 on: March 11, 2009, 06:11:31 PM »
I suspect all the data collected will be used in the development of your new cams. I would figure the new cam design will eliminate any need for the 3-way pinion or the re-phasing. This thread keeps getting better. Keep it coming Ace, It's almost lunchtime!  :P

Blltrdr

Yes, certainly I'm using all the data that I can collect, and observing what happens even with different displacement Bullets.

And I will use all the data available to help in the new cam design.

But the cool thing about the re-phasing is that for a Bulleteer on a budget, they can get some nice results by just making some adjustment to the cams they already have.

And I might even make up some custom cams that are already pre-set to the rephased timing, to make it easy for people to do it. Just like Luoma suggested.
There's really no reason why not. It's an effective cam timing that people might like, and if they can just drop them in, then they don't have to fuss around with all the dial-indicator work.
The only downside is that they would cost as much as any cam set costs, because they'd be new custom cams. But, they'd work well, and this is now certainly a proven fact. So, that's another possible option.

The new cams that I'll make for the Mondello head will be much more specifically targeted at exactly how that head flows, so they will be somewhat different. And probably be about the same cost.

But, variety is the spice of life, and different strokes for different folks, and all that jazz.
So, perhaps I can do both. Some people won't want to spend what it takes to get the Mondello head, and I can produce something that works well for a stock head.
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Re: Let's talk about cams.
« Reply #61 on: March 11, 2009, 06:22:13 PM »
 Ace, how would the re-phasing work with a stock engine whose head had been lapped to eliminate the gasket? Would there be enough compression to take advantage of the re-phasing? You have mentioned before that the re-phasing mimics the duration of the original Redditch cams; what was the compression ratio on those engines?

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Re: Let's talk about cams.
« Reply #62 on: March 11, 2009, 06:44:15 PM »
Ace, how would the re-phasing work with a stock engine whose head had been lapped to eliminate the gasket? Would there be enough compression to take advantage of the re-phasing? You have mentioned before that the re-phasing mimics the duration of the original Redditch cams; what was the compression ratio on those engines?

Blltrdr

Not enough static compression with a stock engine to work with that late of an intake valve closing angle.  I'm not sure about the Redditch cam which the rephased timing is derived from. It might be the "S" cams or something which went with a bike that had more compression. The Redditch cam specs are a little sketchy, and I've received some conflicting info about them, possibly relating to different cams that they produced.
But the stock Redditch Bullets had 6.5:1 compression.
And I can tell you for sure that 6.5:1 will not support this late intake valve closing timing with the 32mm Indian-made cylinder head. You need at least 8:1, and probably the 8.5:1 is the best option. Even 9:1 wouldn't be out of the question.

And the stock piston isn't really up to doing what we want to do anyway. We need a piston change, and the 8.5:1 item seems to fit the bill.

I'd like to say you could do it with a stock piston, but the numbers don't add up.

What I'd really like to do, but don't know if I will, is to make a superlight piston with a shorter height with a relocated wrist-pin hole, that has about 10:1 static  compression ratio and a good quench area, and use that with a late intake valve closing timing to produce a dynamic compression ratio of about 8:1 when running.
That would give great results and still run on 92 pump gas. But it would need the Hitchcock's crank to handle that. And the barrel would have to be shortened some.

Ya know, I did some figuring the other night, and if we de-stroked the crank down to around 3" stroke, and used the 87mm bore size, we'd have a short-stroke 350. Of course the barrel would have to be cut way down shorter to do that.
But, piston speeds would allow revving to 8000 rpms, and with proper porting and camming, it could produce over 40hp as a 350 in a configuration like that. It would be a little wild for street use, but it's interesting.
« Last Edit: March 11, 2009, 06:54:12 PM by ace.cafe »
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Re: Let's talk about cams.
« Reply #63 on: March 11, 2009, 09:47:59 PM »
Not enough static compression with a stock engine to work with that late of an intake valve closing angle.  I'm not sure about the Redditch cam which the rephased timing is derived from. It might be the "S" cams or something which went with a bike that had more compression. The Redditch cam specs are a little sketchy, and I've received some conflicting info about them, possibly relating to different cams that they produced.
But the stock Redditch Bullets had 6.5:1 compression.
And I can tell you for sure that 6.5:1 will not support this late intake valve closing timing with the 32mm Indian-made cylinder head. You need at least 8:1, and probably the 8.5:1 is the best option. Even 9:1 wouldn't be out of the question.

And the stock piston isn't really up to doing what we want to do anyway. We need a piston change, and the 8.5:1 item seems to fit the bill.

I'd like to say you could do it with a stock piston, but the numbers don't add up.

What I'd really like to do, but don't know if I will, is to make a superlight piston with a shorter height with a relocated wrist-pin hole, that has about 10:1 static  compression ratio and a good quench area, and use that with a late intake valve closing timing to produce a dynamic compression ratio of about 8:1 when running.
That would give great results and still run on 92 pump gas. But it would need the Hitchcock's crank to handle that. And the barrel would have to be shortened some.

Ya know, I did some figuring the other night, and if we de-stroked the crank down to around 3" stroke, and used the 87mm bore size, we'd have a short-stroke 350. Of course the barrel would have to be cut way down shorter to do that.
But, piston speeds would allow revving to 8000 rpms, and with proper porting and camming, it could produce over 40hp as a 350 in a configuration like that. It would be a little wild for street use, but it's interesting.

 I guess i am trying to visualize the best route to go for someone not wanting to pony up for the crank & rod and split the case scenario. Someone who just needs to replace there stock barrel & piston with say, the upgraded alloy barrel w/ 8.5:1 piston. Is the re-phasing feasible or is it just to much for the bottom end to handle? It would be great to fill the need for every price point out there, from the budget minded to the guy with the wheelbarrow full of cash. It would be fun to start the discussion from mild to wild and see just how far it goes.

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Re: Let's talk about cams.
« Reply #64 on: March 11, 2009, 10:35:46 PM »
Not enough static compression with a stock engine to work with that late of an intake valve closing angle.  I'm not sure about the Redditch cam which the rephased timing is derived from. It might be the "S" cams or something which went with a bike that had more compression. The Redditch cam specs are a little sketchy, and I've received some conflicting info about them, possibly relating to different cams that they produced.
But the stock Redditch Bullets had 6.5:1 compression.
And I can tell you for sure that 6.5:1 will not support this late intake valve closing timing with the 32mm Indian-made cylinder head. You need at least 8:1, and probably the 8.5:1 is the best option. Even 9:1 wouldn't be out of the question.

And the stock piston isn't really up to doing what we want to do anyway. We need a piston change, and the 8.5:1 item seems to fit the bill.

I'd like to say you could do it with a stock piston, but the numbers don't add up.

What I'd really like to do, but don't know if I will, is to make a superlight piston with a shorter height with a relocated wrist-pin hole, that has about 10:1 static  compression ratio and a good quench area, and use that with a late intake valve closing timing to produce a dynamic compression ratio of about 8:1 when running.
That would give great results and still run on 92 pump gas. But it would need the Hitchcock's crank to handle that. And the barrel would have to be shortened some.

Ya know, I did some figuring the other night, and if we de-stroked the crank down to around 3" stroke, and used the 87mm bore size, we'd have a short-stroke 350. Of course the barrel would have to be cut way down shorter to do that.
But, piston speeds would allow revving to 8000 rpms, and with proper porting and camming, it could produce over 40hp as a 350 in a configuration like that. It would be a little wild for street use, but it's interesting.

 I guess i am trying to visualize the best route to go for someone not wanting to pony up for the crank & rod and split the case scenario. Someone who just needs to replace there stock barrel & piston with say, the upgraded alloy barrel w/ 8.5:1 piston. Is the re-phasing feasible or is it just to much for the bottom end to handle? It would be great to fill the need for every price point out there, from the budget minded to the guy with the wheelbarrow full of cash. It would be fun to start the discussion from mild to wild and see just how far it goes.

Blltrdr

Ok, I hear ya.

Do the 8.5:1 piston and alloy barrel in 84mm bore(500cc) to keep the weight of the piston down. The 535 can give a couple horses more, but the piston is alot heavier and will stress the stock rod more when you use the higher revs. So the 84 bore is easier on the stock rod.
Rephase the stock cams as discussed. Or wait for my cams.
Get the Mondello head and the carb that I finally decide on, which is very likely to be the 32mm Mikuni flat-slide, but not certain yet. Or use a stock head with a good valve job, and a 30mm flat slide from CMW(for ease of installation and jetting).
Upgrade your clutch to the 5 plate, or get the strong springs, cuz you'll need it.
Use the Power Arc ignition., and set up a way to switch in the retarded curve when you need to.
Get a tach, and limit your revs to 5500 rpm.

What's it gonna produce? Don't know yet, because I have to see the data from Mondello on the breathing of the head.
But, with a stock head that has some smoothed ports and a good 3-angle or 5-angle valve job, and rephased cams, and the 8.5:1 piston and a 30mm flat-slide and good exhaust system, you should be good for around 30 ft/lbs of torque, and about 30hp at the rear wheel.

Expect to have a somewhat reduced lifetime of the bottom end, especially the main bearings. So plan a rebuild to beef up the bottom end, as soon as it is feasible for you to do that.

If you can't get the Mondello head, but want some lower cost headwork, contact me and I can work something out for your stock head improvement.
« Last Edit: March 11, 2009, 10:53:02 PM by ace.cafe »
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Re: Let's talk about cams.
« Reply #65 on: March 11, 2009, 11:12:27 PM »
 If the piston weight puts to much unneeded stress on the bottom end then why not have it machined to shed some weight or have a piston made by Aria with correct specs to alleviate those problems. They have an easy to fill out order form: www.ariaspistons.com/products/orderform.pdf. I would think that one could put together a top end that would give a sufficient power band and be easy on the bottom end too. I think your suggestion to use the PWK is a good one; a simple affordable carb with reasonable performance. Save the big gun for your Four-Aces motor!

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ace.cafe

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Re: Let's talk about cams.
« Reply #66 on: March 12, 2009, 12:23:41 AM »
If the piston weight puts to much unneeded stress on the bottom end then why not have it machined to shed some weight or have a piston made by Aria with correct specs to alleviate those problems. They have an easy to fill out order form: www.ariaspistons.com/products/orderform.pdf. I would think that one could put together a top end that would give a sufficient power band and be easy on the bottom end too. I think your suggestion to use the PWK is a good one; a simple affordable carb with reasonable performance. Save the big gun for your Four-Aces motor!

Blltrdr

Yes, there have been various piston makers try to do the 87mm piston.
The lightest one is the forged one from CMW, as far as the high compression pistons are concerned. It's a very good piston, and as light as any maker has been able to do, considering the design it has to conform to.
Unfortunately when it gets bigger to the diameter of 87mm, it gets 25% heavier than we'd really like it to be. That's why I suggest the 84mm piston. when using the stock rod.

Believe me, I am aware of the issues involved with this piston thing.
I will by trying to get something done in that area. It's not as easy as it might seem.
But, it's on the list, and we'll see what we can do.
I've had initial discussion with Joe Mondello about it, and he says he can get something special done by his vendor that supplies the pistons for his Pro-Stock racing engines. We'd like to raise the pin location, so we can make the piston shorter, and also reduce the piston rock that we currently have to deal with. But this would mean shortening the barrel height, which we can do. But, it complicates matters, because it's no longer just a "drop-in" modification when you have to shorten the barrel.
But that could kill a few birds with one stone.







« Last Edit: March 12, 2009, 01:29:56 AM by ace.cafe »
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Re: Let's talk about cams.
« Reply #67 on: March 19, 2009, 02:36:24 AM »
Check out these hp and torque curves from the guy in the UK who re-phased his cams on his 350 Bullet.
The green lines are the baseline when he brought the bike in to the dyno shop.
The blue line is what they got on the dyno tune, with adjustments of the carb jetting and the ignition timing.
This also really shows how important it is to have your bike tuned right. There was a huge increase in power seen after they get the jetting and the ign timing tuned in.
The top chart is hp, and the bottom chart is torque.

Can you believe how broad and flat these power curves are??!! :o
This little 350 has alot of power at almost every rpm that you'd ride at. Those curves come right up high real early, and they stay there. It's pretty awesome!
This 350 would whip most 500 Bullets. It has as much hp at 2500 rpm as a 500 Bullet with free-flow exhaust and filter has at 4000 rpm. And it has more hp than the 500 at peak too, by a small amount. But this 350 gets it so much earlier and hangs onto it for so long, that it's pretty amazing. It would eat a stock 500 Bullet alive, and give a kitted 500 a fit too.

Horsepower


Torque



And here's a chart of hp curves for a stock and modded 500 for comparison.
« Last Edit: March 19, 2009, 03:11:33 AM by ace.cafe »
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Re: Let's talk about cams.
« Reply #68 on: March 19, 2009, 03:08:59 AM »
 So Ace, I would suspect that each grid to the right is 1k RPM increments. If that is so then these are some very impressive results. The HP stays consistent for about 3500 RPM's and the torque is in the same ballpark. What is that RPM range on the dyno sheet.

 These results have got to put a smile on your face, they're quite incredible. How about the guy with the 612 is he going to dyno his bike? That would be very interesting to see.
#'s #'s #'s we can't get enough #'s!

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« Last Edit: March 19, 2009, 03:18:00 AM by Blltrdr »
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Re: Let's talk about cams.
« Reply #69 on: March 19, 2009, 03:46:37 AM »
 Well, even in 500 RPM increments the smoothness the power is developed is awesome. Like you said, the power is developed at the perfect operating RPM range. Should be a blast to ride! What mods have been done to this 350 Ace?

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Re: Let's talk about cams.
« Reply #70 on: March 19, 2009, 04:20:11 AM »
 Well keep up the posts on all these re-phasers you are working with. If the results of this dyno could be had on a consistent basis for all the different displacements then the re-phasing should be standard procedure when installing a high compression piston.

 Kind of getting off the subject I saw a picture of a CB 450 engine in a Rickman frame and thought it looked like a good candidate to put in a Bullet frame. What do you think?

Blltrdr
« Last Edit: March 19, 2009, 04:38:04 AM by Blltrdr »
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Re: Let's talk about cams.
« Reply #71 on: March 19, 2009, 12:47:29 PM »
Well keep up the posts on all these re-phasers you are working with. If the results of this dyno could be had on a consistent basis for all the different displacements then the re-phasing should be standard procedure when installing a high compression piston.

 Kind of getting off the subject I saw a picture of a CB 450 engine in a Rickman frame and thought it looked like a good candidate to put in a Bullet frame. What do you think?

Blltrdr

Well, the rephasing would normally be possible along with the intstallation of the hi-comp piston. But I'm not sure that everyone wants to play with cam timing. However, I'm contemplating a making cam sets with re-phased timing on new cams for people to drop in. With maybe a couple of other needed improvements, like ramp change to deal with the excessive tappet strike when hot.

Looks to me like that CB450 would fit.
I'm not a big fan of doing stuff like that.  It just makes me cringe. But it's one way to get cheap horsepower.
« Last Edit: March 19, 2009, 12:59:24 PM by ace.cafe »
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Re: Let's talk about cams.
« Reply #72 on: March 19, 2009, 01:34:00 PM »
Well, the rephasing would normally be possible along with the intstallation of the hi-comp piston. But I'm not sure that everyone wants to play with cam timing. However, I'm contemplating a making cam sets with re-phased timing on new cams for people to drop in. With maybe a couple of other needed improvements, like ramp change to deal with the excessive tappet strike when hot.

Looks to me like that CB450 would fit.
I'm not a big fan of doing stuff like that.  It just makes me cringe. But it's one way to get cheap horsepower.

 Well a new streetable re-phased camset will be optimal. I myself would never stuff a Japanese twin into a Bullet frame, just saw a few posts a while back about that SX650 engine in a Bullet and ran across this picture and thought it could be done quite easily if someone was wanting and willing. There seems to be a lot of interest in putting a vertical twin in the Bullet, I've read about it often. Some people are hoping & praying that one day soon RE is going to produce a new twin; I say wishful thinking at best. Think about all those diehard's waiting for the new GTO and look what the factory came up with, talk about cringing!

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Re: Let's talk about cams.
« Reply #73 on: March 19, 2009, 02:17:02 PM »
Well, the rephasing would normally be possible along with the intstallation of the hi-comp piston. But I'm not sure that everyone wants to play with cam timing. However, I'm contemplating a making cam sets with re-phased timing on new cams for people to drop in. With maybe a couple of other needed improvements, like ramp change to deal with the excessive tappet strike when hot.

Looks to me like that CB450 would fit.
I'm not a big fan of doing stuff like that.  It just makes me cringe. But it's one way to get cheap horsepower.

 Well a new streetable re-phased camset will be optimal. I myself would never stuff a Japanese twin into a Bullet frame, just saw a few posts a while back about that SX650 engine in a Bullet and ran across this picture and thought it could be done quite easily if someone was wanting and willing. There seems to be a lot of interest in putting a vertical twin in the Bullet, I've read about it often. Some people are hoping & praying that one day soon RE is going to produce a new twin; I say wishful thinking at best. Think about all those diehard's waiting for the new GTO and look what the factory came up with, talk about cringing!

Blltrdr

I've noticed the discussions about twins too.
There's a few different ways to skin the cat.

Let's look at an Interceptor twin engine, which was known "in the day" to have plenty of power for a 750 twin, and fits right in our Bullet frame.
Alright, it has about 52hp, or somewhat less as a Super Meteor or Constellation.
But, let's take the 52hp.

It weighs about 90 pounds more than a Bullet at 450 lbs. And it's wider and more top-heavy than a Bullet, and it costs more to work on than a Bullet.
It's weight-to-power ratio is about 8.65:1.

The Bullet can be made to have about 40hp at the rear wheel as a 612(dynoed and proven), and I'm shooting at doing that similar power level with the 535 in streetable form, and I think I can do it.
At 350 pounds, a Bullet with 40rwhp has 8.75 weight-to-power ratio.
Very close to an Interceptor twin.

Yes, the Interceptor will be a touch more powerful, and just a touch faster, but will be less nimble and more "weighty" to move around.

In the Cycle Magazine test of the Interceptor, it managed 106mph as a top speed, even though it claimed top speed of 117 mph.
A Bullet can do that with a 19T gear on it, or do 102mph with an 18T at 6k rpm, if it is modded to around the 40hp level. So, top speeds are also in the same ballpark.

Essentially, it's within spittin' distance of an Interceptor, with  the nimbleness and low weight advantages of the Bullet.

I thought about putting an Interceptor engine in my Bullet at one time, but after cranking those numbers, I just didn't think it was worth the effort.
I think a properly modded Bullet would be just as good, or better.
« Last Edit: March 19, 2009, 02:22:13 PM by ace.cafe »
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head Conversion. Pistons, cams, etc. Highest performance Bullet engine mods available anywhere.  AVL mods available. UCE kit coming.

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Blltrdr

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Re: Let's talk about cams.
« Reply #74 on: March 19, 2009, 03:06:43 PM »
 Well Ace I am glad you decided to develop the single. I think a lot is determined from the sounds an engine makes that draw it's faithful to it.
 I don't know if you watched the youtube vid of CJay's 612 start up and idle but it makes the desire for a 612 conversion seem necessary. But I will bide my time and see what excellence you bring to the table. I like everything you have discussed and believe you have thought everything through and are on the right track to developing a high performance Bullet that is very streetable and dependable.
 I like your idea of destroking the motor some. How much? You said that the barrel will have to be shortened; can you make up some of the difference in machining the case? I have read that some problems develop because of the way the barrel sits on the case. Now if you machine this surface true you would eliminate this potential problem. I think this could be part of your process of building a very bulletproof motor. What you say?

Blltrdr
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Re: Let's talk about cams.
« Reply #75 on: March 19, 2009, 11:59:57 PM »
The final roadgoing Bullets built by the old uk RE ( not the Crusader based unit Bullet)
had modified cams,possibly the S type used in the scrambles engine, ran a compression ratio of 7.75:1 and had a claimed power output of 21bhp for
the 350, a contemporary road test showed a one way best of 88mph and
an average top whack of 81mph for the 350.Claimed figures for the 500 big head
were 27bhp and 92mph.
The contempoary Velocette Viper/Venom were a fair bit quicker so it might be
worth studying the velo M17/7 AND M17/8 cam profiles.
If anyone has an older copy of tuning for speed there are some interesting suggestions for making your own steel conrods using welded fabrication
I believe this was done on the GMS specials built in the 1950's.
When I tuned my 350 I fitted an R profile exhaust cam obtained from Keith
Burton and on his advice kept the stock intake,the piston used was an
original RE item and I think was about 7:1 throwing away the head gasket
and lapping the joint brought it up to just abou 8:1.Top whack improved
from just over 70 to just about 80.
Love all the suggestions for improving the engine you might just re-invent the
Continental GT with that sort stroke engine.

jonapplegate

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Re: Let's talk about cams.
« Reply #76 on: March 20, 2009, 03:18:35 AM »
You know at this point might it be beneficial to explore what can be done to reduce parasitic power losses and try to maximize the power transferred to the rear wheels.
 Does anyone have data on power at the engine as to power at the rear wheels? What can be done to minimize the loss?

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Re: Let's talk about cams.
« Reply #77 on: March 20, 2009, 07:34:57 PM »
 Full roller valve trains are also of interest to me not only because they reduce frictional losses but mostly because the tend to last a lot longer when properly designed and maintained.
I can break it better,,,,at night, in the rain, on the trail,, 20 miles from nowhere.

REA #136

"TIMEX", the '06 Iron Barrel Military that takes me everywhere I want to go... and some places I shouldn't.

ace.cafe

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Re: Let's talk about cams.
« Reply #78 on: March 20, 2009, 08:22:51 PM »
Full roller valve trains are also of interest to me not only because they reduce frictional losses but mostly because the tend to last a lot longer when properly designed and maintained.


If I can figure out a way to make them work with the .012" expansion ratio in our tappet clearances, they are definitely on the table.

However, if they cannot be used for whatever reason, our existing tappets are mushroom tappets, which if worked correctly can give lift rates very near to rollers, without the disastrous failure prospects of rollers.
So, I'm looking at both options.

There is a DLC coating available which may give the solution, if used on the mushroom tappet faces and cams. Looking at all the options right now.
I would love to get rollers in there if I can.
I'll see what Mondello has to say about it.

There will definitely be new tappets supplied with the cams, and I'm going to use whatever I can to get those cam flanks up as high as I can, as early as I can.
« Last Edit: March 20, 2009, 08:27:03 PM by ace.cafe »
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head Conversion. Pistons, cams, etc. Highest performance Bullet engine mods available anywhere.  AVL mods available. UCE kit coming.

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Ice

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Re: Let's talk about cams.
« Reply #79 on: March 21, 2009, 04:31:50 PM »
I wonder if its theoretically possible to make UCE hydraulic roller lifters work.
I can break it better,,,,at night, in the rain, on the trail,, 20 miles from nowhere.

REA #136

"TIMEX", the '06 Iron Barrel Military that takes me everywhere I want to go... and some places I shouldn't.

ace.cafe

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Re: Let's talk about cams.
« Reply #80 on: March 21, 2009, 04:51:29 PM »
I wonder if its theoretically possible to make UCE hydraulic roller lifters work.


No, we have no oil pressure feed to the tappet guides. And even if we could route some special lines to them, our oil pressure is too low to work them  properly.

However, there are some solid roller tappets which might be able to work, and I'm doing further investigation about them

Our current tappets are solids that look almost exactly like a valve. Narrow shaft and a big round head. Pretty large face mushroom tappets. And mushroom tappets can get very close to the performance of rollers, in terms of aggressive lift potential. And with our limited lift situation, we may be served just as well by the mushroom solid lifters like we have.
But, there is at least  room for improvement on the friction on the faces, which could be improved by a suitable roller tappet, or by using a modern ultra-hard friction-reducing coating such as a "Diamond-Like Coating"(DLC). And there are some other ceramic type coatings with can do similar purpose.

Basically, if we can get a good roller in there, I'll do it. If we are forced to use our existing style mushroom tappets, we aren't far off the performance of a roller tappet with those, and we can get them coated to do the friction reduction. And that may be the lesser cost option, with as much gain as we need to get.
The mushroom tappet is the next best thing, aside from a roller so it's a good performance system if you make a cam that utilizes the mushroom head diameter capacity to the fullest.
And our mushroom heads are much larger than the racing solid mushroom tappets that are still used by modern racers today. Bigger than the racing mushroom tappets sold for GM, Ford, Mopar, or even AMC. And the larger the head, the more like a roller it is, and the more you can get from it..
Our tappets really aren't bad. They just need optimization.
I'll use make them as optimally as possible, and grind the cams to make the most of them, if a roller isn't viable.
« Last Edit: March 21, 2009, 04:57:08 PM by ace.cafe »
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head Conversion. Pistons, cams, etc. Highest performance Bullet engine mods available anywhere.  AVL mods available. UCE kit coming.

Please visit my new website:
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Ice

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Re: Let's talk about cams.
« Reply #81 on: March 21, 2009, 06:58:06 PM »
Thanks Ace. I do believe the friction reduction will be of real interest and value to all.
Weather building for permanence or longevity the benefits should outweigh the cost.
« Last Edit: March 21, 2009, 07:03:16 PM by Ice »
I can break it better,,,,at night, in the rain, on the trail,, 20 miles from nowhere.

REA #136

"TIMEX", the '06 Iron Barrel Military that takes me everywhere I want to go... and some places I shouldn't.

Chuck D

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Re: Let's talk about cams.
« Reply #82 on: February 18, 2013, 12:33:17 AM »
One more.
2006 Bullet Sixty-5 w/ Ace "Fireball 535" Kit (#10)
Ace "GP" head in the works.

'76 Honda CB550Four K(sold)


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