I did a compression test on my 94 Spirit with 37500 miles. I ram it for about 3 minutes then shut it off. Each one read right around 170 PSI after 8 cycles. What was the original PSI for compression when they were new?
Man, I've been all through my Haynes manual and there is no information in it at all for running a compression test and specs for what the readings should be. I'd say if they're all at 170, you're in great shape. I'm guessing that even new, it's probably 170 to 180 anyway.
I checked a service manual for 1989 Acclaim / Spirit. Minimum compression given for each cylinder of the 2.5L engine is 100 psi with no individual cylinder varying more than 25%. No maximum nor ideal compression specification was given. So if you have consistent pressure of 170 psi across all cylinders, the engine is "like new". You are in great shape.
170 is way high. Should be between 130 and 140 new.
Two things cause high compression - heavy carbon buildup, and cam timing advanced a tooth or more. When a mechanic accidentally advanced it a tooth while changing the timing belt, my compression went from 135 to 150.
You're going to be running into head gasket problems with compression that high in a 2.5... I know, I'm in the same boat as Bob, except my advance was intentional. As long as compression is above 100psi and even over the cylinders, you're fine. My cylinder bores are like new (still have crosshatch after nearly 120k) and I'm not anywhere near that. I can't remember exactly what the numbers are.