Compression Ratio

[Hawaiian]

What is the clyinder ratio for 150 lbs per cylinder(i.e. 8 to 1)

[oldphart]

Sorry, it doesn't work that way. Ive had 12.5-1 motors pump 175 LBS and Ive seen stone stock smogger ohc 4 cylinder Fords pump 225 lbs. a lot has to do with your cylinder sealing and cam size. A forged piston engine thats cold will pump low numbers cause the pistons have to expand to seal the hole. Cams with a lot of overlap and small lobe centers will pump low also. about the only way to accuratly come up with compression ratio is to cc every thing. cylinder pressure numbers are only usefull in determining if you have a problem relative to other holes on that motor.

[lakecrazy]

My 460 with forged pistons, huge cam and 10.5 compression cranks at about 170-175 psi on each cylinder.

[spectras only]

lakecrazy,like oldphart says,it's a good test for checking the percentage between cylinders.175 sound fine,if you pour some oil in all the cylinders you may read as high as 200-225.