Piston pop-out?

knighty

Member
is it OK to machine down a blocks deck face, so the piston pops out the top about 0.020"-0.025" ???......or is this considered asking for trouble? Power is in the region of 14-20hp in the region of 8-9000rpm.

I know people machine them so the piston is down a bit or flush, but for some of the tuned motors I build we are struggling for CR and the 0.040" fibre gaskets really do not help reduce volume.

I'm struggling to see why it wouldn't work.
 
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knighty

Member
Clearance as you know is the only issue I see .
Y'all can't get the .009 gaskets ?
Yes I use the thinner steel-laminate gaskets all the time on low-power 7hp gx160 engines, but they cannot handle the higher pressures on 14-20hp motors, they blow out rather easy.
 

1fasttiller

Member
I think you're asking for trouble with pop up anything over .010" . You need to be using the thinner gaskets with O ringing and also milling the head and/or welding the CC to get your compression up.
 

IndyHarry

Member
If you got one of those special thick dome pistons, you could maybe carve the top to clearance or fit inside the 22cc combustion chamber while maintaining the .030" piston to head clearance. Might have something then. Who knows. I think ARC sells the long rod thick dome kit but everybody fly cuts .090" level instead of contouring to combustion chamber.
 
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