Ok I have never done a compression test before so my question is how do i determine if the compression is accurate or not. I know how to do the actual test but what is the equation that needs to be done to find correct compresson ratio?
compression ratio is different from what a compression test will determine. compression ratio is just the ratio of the volume of the cylinder/combustion chamber at BDC versus TDC. a compression test will show you if any cylinder is losing air/fuel through the rings, gaskets, valves, etc.
Its not for my mustang its for my Mopar its a 440, so I guess if I do the compression test and all cylinders are reading correctly I thinks it has to be more than 80% of 200 p.s.i. then my total compression should be what the manual says.