Nothing at all. I'm doing some diagnostic work on my buddy's 91 camaro. Before I run a compression test I would like to know the right ratio. I imagine it's going to be low, it has like 100,000 miles on it. Without regular oil and maintenance stuff.
If you are doing a compression test at least 90 psi is needed for combustion I believe but ya probably wanna be at least 120 or better with that kinda mileage. what seems to be the problem???