So I just did a compression test on my new-to-me 1997 Spec Miata. Car has 51k miles and I believe this is the original motor. Engine runs fine with no obvious signs of problems. I followed the standard procedure for a compression test and these are the results:
Results (Cyl 1 / Cyl 2 / Cyl 3 / Cyl 4):
Dry: 134, 145, 130, 125
Wet: 148, 149, 138, 135
I don't yet have a shop manual but my understanding is that 182 psi is the "standard" value for this motor.
What could cause all the numbers to be consistently low like this? While cyl #4 is the weakest, the others aren't much better. Maybe head gasket? I don't know.
What can you folks tell from the above results?
Thanks in advance.