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Author Topic: Engine design and modifications Q/A thread  (Read 2527 times)

ace.cafe

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Re: Engine design and modifications Q/A thread
« Reply #45 on: November 24, 2013, 05:44:13 PM »
So what you are saying is that it is ok to match the intake port on the heads to the gasket and manifold as long as I'm just opening the initial edge of the runner on the head?

Scottie

I am surmising by your question wording that your manifold is bigger than the entry to the head?
If that is so, then there may already be a problem.
Ignore the size of the gaskets, they are not sized to be anything related to performance. Make your own gaskets that are the right size.

I can't say if it is okay to open up the port entry to match. Maybe it is, maybe it's not.
I would have to see the rest of the port in question.

We are dealing with a system that begins with the bellmouth, and ends in the cylinder, and every millimeter of that entire system must be designed to work together to achieve the goal. Just "matching the ends" of two parts, when it's likely that neither one is actually the right size for the system, is not getting anywhere.

This is entering an area which is a big issue with people who are just beginning to get into the performance area, and it's very common in Enfield "DIY" circles, where people just "put parts together" expecting something good to happen. I can tell you that is where a lot of people go wrong. If you look at what we do at ACE, the whole system is matched to reach a certain goal.

You need to measure those parts out, find out what the relationships and shapes are like from the bellmouth to the valve, and get some strategy going, BEFORE you cut anything.

Here's some good basic criteria.
Find out your bore size.
The intake valve should be about 53% of the bore diameter.
The exhaust valve should be about 80% of the intake valve diameter, but it might be larger because Enfield commonly used a large exhaust valve. This can be compensated in cam design.
The intake valve throat should be 89% of the intake valve diameter on a typical street application.
The port minimum cross sectional diameter should typically be about 75% of the valve diameter for a port that has the usual angle that an Enfield port has. The carb should be the restriction, for best atomization.

As you can see, this is not even addressing the matching of two parts. The matching of the parts comes in AFTER you know what the sizes and relationships and tapers and shapes need to be. THEN you can match things up.

So, given what I have just explained, IF your intake manifold is larger than the intake port entry at that junction, here is what I would do to it.
I would leave the port alone, if you are not going to do a full porting job.
I would bolt the manifold to the head in such a way that the tops are aligned for best flow, and leave the mismatch at the floor.
Then I would fill the floor of the intake manifold with some JB-Weld, and shape it so that it matches to the port entry nicely, and sand it and finish it with that rough surface finish that we discussed previously. I'm not saying to JB-Weld the manifold to the head, just use the JB-Weld to fill the floor for shaping inside the manifold to match the port floor in the head, for flow matching purposes.
Make a gasket that fits that hole exactly, and use it.
Put it all together carefully with the carb off, so you can see that everything lines up the way you want it to at the junction of the ports, and then put the carb on it.
This gets you the flow match you want, and doesn't cause potential damage to the port entry when you don't know for sure what is going to be needed to be done to the port in the future. We never want to cut ports until we know exactly where we are going with them, because if it gets done wrong, then it's very hard to deal with later on when we want to do it right.
« Last Edit: November 24, 2013, 06:03:51 PM by ace.cafe »
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head . Pistons, cams, etc. Highest performance Bullet engine mods available .  AVL mods. Redditch 700/750 Twin mods. UCE kit soon.

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High On Octane

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Re: Engine design and modifications Q/A thread
« Reply #46 on: November 24, 2013, 07:56:34 PM »
OK.  After pulling the intake back off and taking a closer look at things I realized that the intake ports on the heads are considerably smaller than the gaskets themselves, where as the gaskets are pretty close to the same size as the ports on the intake.  So I decided to not do anything in that department as it is going to take a considerable amount of work to match the intake, and rather wait until I have you do these heads and build a pair of custom dual intakes like we've spoken about.

Now on the carb side, as I had mentioned the port on the carb flange for the manifold was slightly smaller than the opening of the carb at the top and bottom, so I definitely wanted to address that.  I took the Dremmel and very carefully removed maybe .25mm off of the opening of the top and bottom.  I also had a brand new thick paper gasket so I went ahead and trimmed that up to perfectly match the intake opening.  I also noticed there was a bit of a lip protruding about 3/4" in from the flange opening on the outer side of each runner so I went ahead and removed those as well.  I then took 80 grit paper and smoothed out my grinding marks by wet sanding.  Then I took 180 grit paper and a piece of tubing and sanded in a circular motion down the runners.  After that I took a very small wire brush wheel in my drill and at a slow speed made spiraling motions down each runner.

Does seem acceptable and correct?









Scottie
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ace.cafe

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Re: Engine design and modifications Q/A thread
« Reply #47 on: November 24, 2013, 08:13:53 PM »
Matching up the manifold and carb was good.
As for the step-down at the manifold/ head junction, that will need to be addressed at some point in the future. Just let that be for now.
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head . Pistons, cams, etc. Highest performance Bullet engine mods available .  AVL mods. Redditch 700/750 Twin mods. UCE kit soon.

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gremlin

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Re: Engine design and modifications Q/A thread
« Reply #48 on: November 25, 2013, 05:50:29 AM »
............. So, if you ever wondered about something, I'll try to answer to the best of my ability.

concerning the UCE engine, Electra piston, and squish.

Is the compression height of the stock UCE and the stock electra piston the same ?   Are there any clearance issues with this combo ?  how much does it raise the compression ?
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ace.cafe

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Re: Engine design and modifications Q/A thread
« Reply #49 on: November 25, 2013, 01:42:39 PM »
concerning the UCE engine, Electra piston, and
Is the compression height of the stock UCE and the stock electra piston the same ?   Are there any clearance issues with this combo ?  how much does it raise the compression ?

I haven't worked on an Electra, but it is my understanding that the compression height and compression ratio are the same as the UCE. The combustion chamber appears to be the same too, and the valve lift height too.

So, I would surmise that that AVL piston should be compatible withe the UCE. However, there might be bore clearance issues if trying to drop it into the same hole , without using an over bore size piston and boring to suit.
I would not expect any real compression change with this swap, but I don't know if there are any small differences in the dish volumes.

Apparently,  Scooter  Bob says that the AVL 535 flat top piston will drop right in and work with no issues in a 535 bored cylinder. That will have some compression increase due to the bigger displacement compressing into the same chamber, along with a flat top reducing the working chamber volume. I don't have the dish volume figure so I can't say exactly how much compression increase.

Regarding squish, the examples of UCE which we have seen, and AVL which we have seen reports about, did not get the piston close enough to the head for proper squish distance. I haven't measured the piston-to-valve clearance over TDC with the stock piston yet, so I can't tell you how much clearance there will be. The stock lift is very low, so I would suspect no contact problem there, using stock cams, but doing a clearance check with clay on the piston is advised whenever moving the piston or valve closer together over TDC.

GHG reported that after some minor shaving of the barrel height, he got the squish distance to just about .060", which is the largest acceptable squish distance, and is very marginal in operation.
The range for squish is from .020" to .060" distance from the head. The minimum recommended by the NHRA for squish on stock class engines is .021". If you get near .060" the squish is barely working, and might not be working. The sweet spot is around .040" squish distance from the head.
Any squish distance bigger than .060" and less than .100" is a "danger zone", where there is a propensity to increase the likelihood of detonation. So, if it is more than .060" it needs to be moved even further away than .100" or it may be a problem. Or, you could bring it closer, so it's in the squish range.
« Last Edit: November 25, 2013, 03:22:33 PM by ace.cafe »
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head . Pistons, cams, etc. Highest performance Bullet engine mods available .  AVL mods. Redditch 700/750 Twin mods. UCE kit soon.

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jedaks

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Re: Engine design and modifications Q/A thread
« Reply #50 on: January 14, 2014, 12:50:39 PM »
Hi Ace, I have a question about ignition systems.

I have kept the points ignition, partly for sentimental "traditional" reasons and for the ability to do roadside repairs/replacements if ever necessary. They have a get-you-home fiddle factor to them.

I'm also aware the modern electronic ignition sytems are very reliable and once the timing is set then it is set for good and you can forget it. (I've been told if a bike with e-ignition ever pings, it has to be due to fuel mixute and not timing.) Consequently, I am guessing, fuel economy and power generation are better.

But, how much better? Are those of us still using contact breaker points ignition missing out on very many benefits? Would a town/country commuter Bullet doing 30 klm a day really be improved over old fashioned points?

I'm not convinced about value for money.

Thanks
« Last Edit: January 14, 2014, 12:53:54 PM by jedaks »

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Re: Engine design and modifications Q/A thread
« Reply #51 on: January 14, 2014, 01:13:56 PM »
Speaking strictly from my own personal experience:

The K2F magneto was bad in my old '58 Twin.  I tried several attempts at replacing the points, the brushes, the HT leads, and I was down to only 2 options.  Either have the mag rebuilt and play the waiting game for how long it would be before it failed again.  Or By-pass it and install electronic ignition.  They were both going to cost $300, so I opted for the Thorspark Electronic Ignition Conversion.  This system uses the existing magneto, but you remove the points plate and replace it with an electronic trigger plate, which sends a signal to an external coil.  All in all it only took about 2 hours to install and set the timing, which brings me to this:


I'm also aware the modern electronic ignition sytems are very reliable and once the timing is set then it is set for good and you can forget it. (I've been told if a bike with e-ignition ever pings, it has to be due to fuel mixute and not timing.) Consequently, I am guessing, fuel economy and power generation are better.


YOU STILL NEED TO HAVE YOUR TIMING CORRECT!  For example, it took me about 6 weeks of micro-adjustments every other day before I had the timing Perfect.  But I'm also a perfectionist and I knew there was more to be gained from where it was at.  Since I got it dialed in, the only issue I had was the screws that mount the trigger to the mounting plate backed off, loosening the trigger and causing a misfire.  A little bit of loctite on those screws and my ignition has been ROCK solid ever since, almost always starting on the first kick regardless of conditions.  Quite easily the BEST $300 I spent on the restoration.  In fact, I don't think I could ever go back to points now.

Scottie
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ace.cafe

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Re: Engine design and modifications Q/A thread
« Reply #52 on: January 14, 2014, 01:24:13 PM »
The problem with the Enfield points ignition is not the points. The points are fine, considering what they are for maintaining etc. They perform the same switching function as any other switch.

The problem is that the mechanical advance system is inadequate to deal with the engine needs in certain circumstances.  This is where a more modern type of ignition system can be an improvement.
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head . Pistons, cams, etc. Highest performance Bullet engine mods available .  AVL mods. Redditch 700/750 Twin mods. UCE kit soon.

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jedaks

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Re: Engine design and modifications Q/A thread
« Reply #53 on: January 14, 2014, 02:12:18 PM »
The problem with the Enfield points ignition is not the points. The points are fine, considering what they are for maintaining etc. They perform the same switching function as any other switch.

The problem is that the mechanical advance system is inadequate to deal with the engine needs in certain circumstances.  This is where a more modern type of ignition system can be an improvement.

Fair point well said. What about the claims that e-ignition improves fuel economy and power?

ace.cafe

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Re: Engine design and modifications Q/A thread
« Reply #54 on: January 14, 2014, 02:46:46 PM »
Fair point well said. What about the claims that e-ignition improves fuel economy and power?
It might, or it might not.
If the previous system caused the ignition timing to be wrong, and the new system caused it to be right,  then power and/or fuel economy might be improved. If the previous system was correctly timed, then no improvements will be seen.
If the old system had a weak coil, and the new system has a strong coil, then that might be cause for some improvement to occur from the stronger spark.
Again, it's not a matter of whether it is "electronic" or not. It's a matter of if the timing is correct. The engine has no idea what kind of controller is being used, nor does it care. All the engine knows is if it's getting the spark at the right time, or not.
It is entirely possible for an electronic ignition to get the timing completely wrong, if the advance curve was programmed by somebody who didn't know what he should know, or if the end user incorrectly set up the timing.

What we know for sure about the stock Enfield ignition is that it swings to full advance almost immediately upon applying any throttle above idle speed, and stays at full advance until returning down to just slightly above idle speed.
If any load is encountered at rpms below torque peak, such as the need to accelerate with a passenger aboard, or climb a hill , or both,  then the system has no ability to retard the spark for these conditions,  and so it then tries to perform the task with the ignition too far advanced. This causes ping, overhearing, and often seizes the piston in the bore.

Some electronic ignition systems might be able to retard the ignition under circumstances like this , but many cannot.

There is no panacea from some nebulous category like "electronic". Each ignition system needs to be considered based on how well it deals with the things that we need it to do.
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head . Pistons, cams, etc. Highest performance Bullet engine mods available .  AVL mods. Redditch 700/750 Twin mods. UCE kit soon.

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Re: Engine design and modifications Q/A thread
« Reply #55 on: January 18, 2014, 05:34:28 PM »
Is there any advantage of long-skirt piston over short-skirt piston with bracing ?
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ace.cafe

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Re: Engine design and modifications Q/A thread
« Reply #56 on: January 18, 2014, 06:02:04 PM »
Is there any advantage of long-skirt piston over short-skirt piston with bracing ?

Yes, a long skirt piston supports the piston better in the bore, and can be better at minimizing piston "rock".
However, a long skirt weighs a bit more, so sometimes it is abbreviated to save weight in performance applications.
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head . Pistons, cams, etc. Highest performance Bullet engine mods available .  AVL mods. Redditch 700/750 Twin mods. UCE kit soon.

Please visit my new website:
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