Piston piece

your compression needs to be checked with the vac advance dissconected and you wanna get a @ idle reading and 3000rpm full/mechanical advance reading then report, otherwise it sounds you're 10.25 is really 8.9-1 or at least the cams bleeding it off [dynamic] to look that way, cause thats a lo of initial to put a load @ low rpm and not ping.

What the cranking psi and the cams @ .050 duration, if you can find out.