If you add up your compression ratio, make sure you know all the details, if your pistons are the common "rebuilder" pistons, they`ll have .020 off the tops. I`m running a .040 350 with 345 speed pro pistons, and these have .020 off the tops, which don`t help compression any. with a compression gauge mine came in at a low 145 psi. when I was using a trw forged flat top of the same design with the same heads it came in at 165 to 170 psi.