I checked the compression on my donor car today to help me in deciding about using the motor or not. All of them checked in about 125. The lowest was 120. Does this sound normal? The car has 55k on it. Do different testers vary? As long as they are all in the same ballpark am I good to go?
If you did the test on a cold engine the numbers are very good. The fact that you only had 5 PSI difference between high and low is also very good. The engine has to be up to operating temp to get best results for a compression test.
if the engine was still warm, the numbers are a little low, but I would run the engine until it started using more that 2 quarts of oil every 1500 miles.
Did you do the compression test with all spark plugs out and at wot? My rebuilt engine has about the same mileage (60k) on it and when I tested it warm I got 150's across all cylinders. A stock compression 5.0 if tested at operating temp has a compression of 180psi new and 140psi at the service limit.