Thee were no 8.8:1 351-Cs. Five (4) possible compression ratios were available: 11:1 in '70, 10.7:1 in '71 (all closed chamber). In the '71 351-CJ with open chamber, it was 9!1, in the '71 Boss (closed chamber), it was 11.7:1 and in all others (open chamber) it varied from 9.0:1 to 9.2:1. Using these numbers requires you to make several assumptions: first, that the block has never been surface-machined. Second, that the heads have never been machined. And third, that you've never had a valve job done, all since new. ANY machining on the castings change the volume of the combustion chamber, and with a near-30-year-old performance engine, those are big assumptions, unless you bought it new & know its history. It also assumes that this is the original engine. The volume of a stock open-chamber head was 73.9 to 76.9ccs in new '72-74 engines, and 61.3 to 64.3ccs for closed-chamber early heads. Volumes for the '71 Boss & HO closed-chamber engines in '71 was 64.6 to 67.6ccs, including production tolerances and with zero carbon build-up. This above is why ALL engine builders measure chambers, blocks, rods etc to calculate compression ratio- all published values are worthless. All the pistons were flat-tops but deck heights varied, too. Finally, the engine really doesn't care what its compression RATIO is, it only cares about compression PRESSURE, which is dependent on cam timing & lift as well as the internal volume of the chamber & stroke. Sorry.
