i have a 350 i am building up for my car, it has trw forged .1 " dome pistons, and im going to but 76 cc, 202 heads on it, i was wondering what you thought the compresion was for them and if you think i can run pump gas, in summit it says that its 9.31-1 compresion with .30 over, but mines std, however the 400 my dad built has flat tops at 10.8-1(64 cc heads) so i was thinking shouldnt domed be around 10-9-1 with a .1" dome? thanks for your help,

 

comparing 350 to 400 compression is like comparing apples to oranges, they are just not the same thing and he is running smaller chamber heads as well so his compression is going to be more for that reason alone i am not real familiar with those pistons but the 9.3 doesnt sound unrealistic to me with 76cc heads on top it might be ok on pump gas if thats really what the compression ratio is with those heads and pistons, the .030 over doesnt affect the ratio too much only would lower it to 9.2 from 9.3
Do you know what the cc or part number of those pistons is?

 

theyre TRW-L2304 STD the have a .1 " dome

 

the overbore actually raises compression a bit . with what summit says (with the 30 over pistons) your probably around 9-1 or 9.1-1. i know the over boring rasing compression sounds wierd but trust me it's right , i just dont remember how to explain it right now. you should be fine on pump gas .

 

I know overboring raises compression, he listed the .030 ratio and I said it would lower it from 9.3 to 9.2

This is the info for that piston

11.26:1 (58cc heads), 10.50:1 (64cc heads), 10.02:1 (68cc heads), 9.59:1 (72cc heads), 9.19:1 (76cc heads)

I guess I hit that pretty close huh?

The cc of the heads is why the compression is so low with those pistons.