w8less

can some explain this to me and whats the difference between flat and dome pistions i am wanting to get some to raise my compressionm with my 302 so i can start working on my 351

95whitecobra

I'll try to do it in laymans terms as there is a formula using the pistons, bore, and combustion chamber to calculate compression ratio. Basically, flat tops pistons are just as they sound "flat". However there really is not a true "flat top" piston as it has to have some relief cut in for the valve clearance. A domed piston increases compression by displacing volume from the combustion chamber. A "dished" piston is just the opposite. A 5cc domed piston used with 61cc heads would be equivalent to a flat top piston with a 56cc head. A -5cc dished piston with 61cc heads would equal a flat top piston with 66cc heads.

1. flat top piston does not alter compression ratio
2. Domed piston increases c/r
3. Dished piston reduces c/r

This is how it was explained to me. I hope it helps.

tinman

A dome ('pop-up') piston has a dome or something like a mountain on the top of it. This will fill the camber and bring the compression ratio up. Up to high for street use in lots of cases.
A 'flat top' piston is just that, it may or may not have valve reliefs machined into the top of it for clearance.
IMHO, horsepower that is truly useable is not that much greater with a high compression (11.0+) than staying below that. Also, with the flat top piston the flame travel is faster and cleaner........

vfast

on and avg street engine will all else equal going up 1 point is like 15 hp-25hp on so

w8less

thanks for the help i understand more about it then what i did but i am going to do some more research about it to get a greater understanding of it