427 so compression test readings

[mr0077]

Mine checks out at about 140 psi across the board, and put out 389 RWHP on a hot day here in Houston...I'm running 10.7:1 with the Comp Cams 292 camshaft. Compression readings are affected by a lot of stuff (compression ratio, valve overlap, cam indexing, etc.), not to mention mechanical condition of engine (rings, valves, etc.). Your readings sound a little low, try what Michael suggested, check it warm, all plugs out, throttles blocked wide open. Bear in mind that if you aren't REALLY fast, the motor will cool during the checking process, and that will affect your readings (so...check four cylinders, put the plugs in and warm it up, check the other four?) Nah, just note that if the last four start to drop off, it could be because of the cooling). If the readings are still low, squirt some oil in the cylinders and see if it bumps up to higher readings (if so, it indicates bad compression rings). Can you run a leakdown test as a backup?
Let us know what you find.