I disconnected the coil and cranked the engine over a few cranks. 150 psi is pretty close from what I've read. I may be under 10:1 some that was original figures and after I checked my valve to piston clearance I never worried about it anymore. Let me run the numbers again and see what I get. I know I was .012 under the deck with 5 cc flattops 65cc heads and a .050 head gasket i think my original numbers was with a .028 head gaskets and I opted for the thicker ones.