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Author Topic: another cam option.  (Read 1415 times)

jonapplegate

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another cam option.
« on: January 03, 2009, 03:14:35 AM »
I would like another option for replacement cams. Something halfway between stock and the first cam option now offered in the catalog. It would be nice to have something a bit bigger but just to bump up the power a bit, not totally change the power curves. Maybe something like the original cam profile only modernized? You know with better curves and such?

ace.cafe

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Re: another cam option.
« Reply #1 on: January 03, 2009, 03:44:52 AM »
Jon,
There is something that can be done, but it's pretty technical, in that you must be able to read your cam timing with a degree wheel and dial-indicator.
Not that hard, really, and the degree wheel and dial indicator are not expensive.

It's called "re-phasing the cams" and it can be done with the CMW adjustable timing pinion in the catalog.

First, you have to check what your existing cam timing is, on YOUR bike. Believe it or not, the cams from the RE factory do vary from one bike to the next, so you have to know where you are starting out from.

The first method is to use the timing pinion to retard the cam timing by 4.5 degrees, using the adjustable timing pinion. This is pretty straightforward, and you could do this without checking your existing timing if you wanted to. It's only a mild change, and retarding the cam timing like that will push your power curve up the rpm range a little bit. This will give a little better extension of your rpm range for more high end power.
It's a fairly crude change, and it would be better if you could just retard the inlet cam, and leave the exhaust cam alone, or even advance it a bit.
This is where the next method comes in.

The other method is a bit more radical, and requires that you check your existing cam timing with the degree wheel and dial indicator.
Assuming your cam timing is about what the spec sheets say, it is possible to retard just the inlet cam by one whole tooth, and then use the adjustable timing pinion to advance both cams by 4.5 degrees.
This gives you about 14.5 degrees more retard on your inlet cam, and about 4.5 degrees more advance on your exhaust cam. The cam overlap is reduced for better cylinder trap, and you get more top end power without the power loss in the lower rpms that happens with the Performance Cam set.

However, this change needs to have the hi-compression piston installed for it to work right, just like the Performance Cam set does.
You can't have a late inlet valve closing event unless you also bump the compression to help it work right. If you don't bump the compression with the hi-compression piston, the cam change will fail to perform due to lack of sufficient compression for the new cam timing.
In any case, the ignition timing must also be retarded by a few degrees too, because the increase in compression and breathing will require that later spark timing, or you'll burn a piston.

Most people don't know what the CMW adjustable cam timing pinion does. It's a mystery to most people about how to use it.
You can get pretty creative with it, but you need to validate what you are doing, by reading and verifying your cam timing when you do stuff like this.

Perhaps I might do a technical thread on this in the future, but if you want to do it, you can contact me by email, and I'll try to walk you thru it.
« Last Edit: January 03, 2009, 03:58:30 AM 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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jonapplegate

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Re: another cam option.
« Reply #2 on: January 05, 2009, 03:17:47 AM »
Thanks Ace, I have the wheel you are mentioning. Very interesting.
   The points I have been trying to make in my recent posts are similiar to something you mentioned. Small increases may not be felt individually but add them all together and you will get a stronger running machine, while not deviating too far from the original performance parameters. I know this is an over simplification. Hopefully I am getting my point across. Engineers who design these machines (engines) Didn't just throw parts at a block and cross there fingers that everything would work together. (unlike the Pontiac Ram Air V, I am a bit of a Pontiac buff) I think this is where many would be engine builders get crossed up. Every Hi-Po part was made with the unspoken understanding that every thing else supporting that piece would be upgraded as well. I hope that anyone dreaming of upgrading performance will not be seduced by the siren song of that one killer piece.
 For street use ,I don't think any of us should be looking for substantial improvement. We should look for ways to increase our mid range. I believe a bunch of small improvements spanning the entire drivetrain will return the most satisfying results.
 Though I speak on a lower level technical wise, Is this what you think as well? I think it is but want to make sure I understand where you are coming from.

ace.cafe

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Re: another cam option.
« Reply #3 on: January 05, 2009, 04:40:13 AM »
Yes, when doing any hi-po work, you have to do all the supporting stuff as well, or you're sunk.

I put a detailed write up for you on the other thread about cams in the Classic Bullet section of the forum.

As a general statement, the Bullet doesn't really respond to what people normally think of as "usual" performance modifications.
It's a bit of a different animal, and takes a specific approach to what will work with it.

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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jonapplegate

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Re: another cam option.
« Reply #4 on: January 07, 2009, 06:03:00 AM »
Thanks for sharing all your obvious technical know how. I for one really appreciate it.