67' 318 crank in a 69' 340

Part of the 340 compression confusion is in some of the aftermarket pistons.... there are some Sealed Power cast pistons, PN 428P, which have 4 valve reliefs but have a compression height that is only .011" lower than the original hi comp pistons. So those are still fairly high compression.

Then the Sealed Power L2385F forged one are 2 valve reliefs but the CH is a full .100" shorter than the high comp ones....