Piston to sidewall clearce

F

Flying pumpkin #31

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Boring a animal block from .020 to .030 over with a world formula forged Piston what should I have for a stock forged piston for side clearance any info would be appreciated
 
racinnut15xm said:
What is max before needing to go next size?
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That depends on how ragged edge you want to live, I guess.
I've had small plate engines run just fine on .0045" clearance. Higher rpm would concern me with that much clearance on an animal piston though. When the piston rocks over TDC, you lose ring seal, to an extent, the more clearance that you run.
 
Back in the day, with similar engines, pistons were fitted pretty loose but with newer low tension rings, it can be a little tighter.
 
CarlsonMotorsports said:
That depends on how ragged edge you want to live, I guess.
I've had small plate engines run just fine on .0045" clearance. Higher rpm would concern me with that much clearance on an animal piston though. When the piston rocks over TDC, you lose ring seal, to an extent, the more clearance that you run.
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with excessive piston clearance, causing piston rock both at tdc and bdc, will you hear knocking sound because of the piston rock at the top?? had a similar question on another post without and answer.
 
Sometimes you will hear piston slap. If you turned the engine over with an electric motor and no valve train, it would certainly be more noticeable. It's difficult to hear that (even with a stethoscope) with exhaust and valve train noise in addition to a small mechanical click twice per revolution.
 
The smaller the clearance the more important precise measuring tools and the resulting measurements are.
 
Jimbo said:
The smaller the clearance the more important precise measuring tools and the resulting measurements are.
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And square and straightness of bore!

Bottom line, if your'e going to run tight clearances, then you had better know what you're doing and have the tools to do the job correctly.
 
steve baker said:
We never run less than .003

Steve
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High clearances reduce friction and enhance performance but reduce dependability. Kaboom, especially on the big end of the rod. On the piston I like around .0023- .0027. I know a local builder that prefers .002 and if you can bore and hone that well, it is probably preferred.
 
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We used to go up to .010 and swedge the piston skirt on flatheads. Don’t know how the would work on an Animal.
 
Very little of what you did on a flathead is useful as a guide to what to do on a Briggs OHV'
I'm not saying that the Briggs OHV's / Animal is utopia because it isn't but many of it's design features are considerably better than the flathead and many other OHV engines.
 
I heard Pete Mueller builds his KT100's with .001" piston clearance. He runs them direct drive and turns 17,000 RPM. I don't know how he gets away with it. But he does! Kinda fast too!
 
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