Jegs shows what I consider to be an incorrect compression ratio estimate for the L2240NF
pistons I mentioned above (Sealed Power now, not TRW).
Jegs list them as having a 21cc dome. If that's correct, with a bore of 4.124", a stroke of 3.76", a 101cc chamber, a gasket thickness of 0.041 and a zero deck height, I get over 10.2:1 CR. Actually too high for a mild cam on pump gas, IMO.
They say its about 8:1. So something is fishy.
In any case, you'll need to cc the heads and measure the deck height and know what the compressed head gasket thickness is to compute your CR. Start w/cc'ing the heads and measuring the deck height.
Then using a CR calculator
, you can figure out what dome volume you need to get the CR you want.