i have a 470 setup i would like to use that has flat top pistons and comes to 11.3:1 how much power will that give up vs. a dome setup of about 10 -15 cc to get to 13-14:1 i would like to keep cost down and reuse the pistons i have instead of buying new and rebalancing rotating asb. but if it is a big loss i will go with new pistons

My :
Keep the flat tops. It's not just the cost of the pistons but the cost of race fuel.

my 511 ci

is a flat top JE piston
7 cc valve releaf
40 th gasket
and indy sr,s 74 cc chambers


is about 12.7 to 1

mill the heads.

I`d keep the flat tops and mill the heads to up the comp. if you need to. Rumor says flat tops have a better flame front and are more efficient at burning up the fuel. I`m at 12.11 comp. and make good power and drive on 91 and mix 91 and 110 when I race.

i have run as much as 42 degrees of timing with domes and 906 heads and as little as 34 with flat tops and better heads. you can order a set of custom thickness cometic head gaskets. i just put on a set of .027[i think] cometics. keep the flats.

Another vote for flats here tooooo .... but maybe even a DISH !! (if you can still keep a decent compression ratio)...I have been told that THAT design can enhance air-fuel atomization.

if the 10 h.p. per point is true i think i will live with 15-25 h.p. less and keep the flat tops just didn't know how much it would loose i didn't know how much the cr would effect hp and tq vs the flame travel on a flat top thanks for the info

there may be an easier way to get that HP you want by picking apart your combination to find the details of where to look.i am sure your engine runs good but i am interested in the parts,tuneup your engine has to make sure you are getting the most from it.there is certainly no shortage of help around here.

400 block 3.90 stroke 4.375 bore 6.76 rod piston comp height is 1.25 0 decked have to run stock heads so i have ported 915 chambers measure 77cc going to roller cam setup with crower cam
int 268 exh is 282 at .050 will go with victor int. and i think a 2 or 2-1/8 header open exh have engine is apart for winter check up and i am planning to install a girdle or go to al. main caps do to the plan of pushing it harder this coming season my heads are o-ringed so milling them would require more work i think how much cr does this need will 11:1 range work ok

did you have the cam advanced at all?
were you going to use spray with that cam?

I dident see anyone mention that flattops are much lighter! my pistons are essentially flattops
that weigh 470 grams a piece