Without knowing the size of the depression in the top of the pistons you are using, I did a quick calculation of the static compression ratio on a 302 using a 4" flat top piston, a head gasket with a "bore" of 4.060 and a compressed thickness of 0.060", your head with no combustion chamber and a stock 4" stroke. Any oversized bore would increase the compression ratio. Adding in valve timing to compute dynamic compression ratio (see explanation here is WAY beyond my pay grade.

Here are some computed static compression ratios varying the distance "down in the hole" to the top of a flat piston.

0.250" 13.83:1
0.300" 12.06:1
0.350 10.71:1
0.400 9.66:1
0.450 8.82:1


How I computed
click here

Last edited by Bill Hanlon; 11/11/2023 3:33 PM.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.