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Author Topic: high ratio rockers  (Read 1164 times)

jonapplegate

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high ratio rockers
« on: January 04, 2009, 09:23:48 PM »
I have been pondering the cam options. Since it seems that there is not an option for a modest cam upgrade then how about Higher ratio rocker arms? I cant recall if you get much increase of duration but you could design something that gave us perhaps 10% more lift? Just a thought.

ace.cafe

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Re: high ratio rockers
« Reply #1 on: January 04, 2009, 10:33:44 PM »
Jon,
I discussed this on the other thread for you.

Short story is it ain't gonna happen.
But, some aftermarket cams can give you that 10-20% more lift.
But, there are some trade-offs with those.

The fact is that a relatively small amount of lift increase is not going to do as much as you might like, is very tough of a fragile Bullet valve train, and the rockers and blocks cannot be moved to provide anything significant in ratio change.
See the other thread in the Classic Bullet section.

I can help you to get the performance changes you may want, but the Bullet is not suited to the normal courses of action in the performance area, so some creative solutions are necessary.
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jonapplegate

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Re: high ratio rockers
« Reply #2 on: January 07, 2009, 12:08:46 AM »
I seem to recall now that High Ratio arms increase stress. Not a big deal in a 90 degree V8 but probably asking for trouble in a Brit designed Motorcycle engine.
 Would I be correct in saying besides the fact you have much less stabilizing strength to work with in a motorcycle application, Brit bikes tended to be designed with no wiggle room? I mean to say that X bike was built to basically handle "x" and thats it. 

ace.cafe

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Re: high ratio rockers
« Reply #3 on: January 07, 2009, 08:47:24 AM »
I seem to recall now that High Ratio arms increase stress. Not a big deal in a 90 degree V8 but probably asking for trouble in a Brit designed Motorcycle engine.
 Would I be correct in saying besides the fact you have much less stabilizing strength to work with in a motorcycle application, Brit bikes tended to be designed with no wiggle room? I mean to say that X bike was built to basically handle "x" and thats it. 

Yes, there's not alot of "fat" in the Bullet engine. It was designed for a particular purpose, and they didn't build-in alot of room for change. But it was very accurately designed for what it was intended to do. The designers of this engine were experts, and did an extremely good job at hitting the intended target, without excess which could have increased costs.

There are some things which we can do with it, and some things which are precluded because there's too much involved to modify.
For example, we could design a whole new engine and have castings made, and then do more things. But, then it wouldn't be a Bullet, would it?
At that point, the prudent thing would be to just buy a Manx. Or perhaps in Interceptor, if you want to stay in the RE stable.

Believe me, if a new rocker design could have been put in there without much difficulty, it would already have been done. If not by others, the group I worked with spent months trying to make that happen, and in the end it couldn't get done reasonably. We do have a design which makes use of bolt-on rocker towers and a new rocker shaft, giving a layout similar to the "Big Head" rocker system, which takes the place of the existing rocker covers, and gives just a little bit more room for ratio-changes and better geometry. And it uses bearings, and a re-routed oiling system. It would cost thousands to have it made up. And in the end, the lift is not changed enough to give us as much as we really want anyway.

The "Big Head" is very good for that type of thing, as it is. But the ports are too big.
So, what you end up with is a "screamer" that goes like hell at 7500 rpms, and is a coughing, spitting pig at normal road riding rpms, and blows its guts out all over the road when the crank or rod lets loose from too much piston speed.
« Last Edit: January 07, 2009, 08:50:33 AM by ace.cafe »
Home of the ACE Fireball 535 Bullet,  and the Joe Mondello Signature cylinder head for the Bullet.

Please visit my new website:
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