What year is the block? there are two compression heights that were used, the early 9.600" and the later 9.577"
Take out the 6.123 rod and the 3.31/2 stroke and you have either 1.822 or 1.799 left for compression height.


It used to be the trick to use 318Poly pistons to raise the compression as most of them run about 1.8.

I was concerned when I opened up my '86 318 and found the pistons 0.055" in the hole. I used the Mr. Gasket 1121G thin gasket which is 0.028" thick. My squish area still worked, testified to by the excellent mileage I got and the complete absence of pinging with 34* total mechanical advance and the lowest grade of gas. The closest that 5.2Mag pistons got to the deck was 0.044 and then you add the head gasket which was probably right at 0.040" compressed height leaving the piston 0.084" down from the squish pads. Yet they worked too.

R.