Pretty impossible to calculate actually. There are so many factors that can affect an engine's psi measurement its not even funny. If you want to find out his C:R there is a list of things you'll need. Bore, Stroke, combustion chamber volume, specs for the head gasket, piston dish CC, deck height.civic_x_95 said:I would do a search but Im at work and dont have time so hopefully someone can help out. I need to know how to convert psi readings to compression ratio. Buddy just built a chevy motor but was wondering what comp he is running.
Dont forget specs on the headgasket and deck height. The compressed head gasket thickness can alter your compression ratio a few tenths of a point. Most head gaskets have a compressed thickness of around .040. Fel-Pro makes one thats .015. Also if a machinist decked the block to 0, then your compression ratio will increase big time, especially on a Chevy block. A stock 350 can have up to .025 shaved off the deck using factory stroke and rods.kommon_sense said:don't think that you can convert between the 2. However your buddy should be able to find out his CR by looking up the size of his combustion chamber and the specs on the dome or dish on his pistons.