The Stovebolt Site Forums The Shop Area Engine Shop Low Compression on Rebuilt Engine

I finally got the chance to perform a first start and break-in run on a rebuilt 1954 Chevy 235.

After the 20 minute breakin run and another 40 minutes at varuous rpms making carb and timing adjustments i ran a compression check on the cylinders and got the results below.

Cylinder 1 was 108 psi
Cylinder 2, 3, 4, and 5 were all was 120-122
Cylinder 6 was 110 psi.

These numbers were much lower than the 130ish psi I was expecting and had a much wider variance than it sounds like I should be seeing.

Should I be concerned enough to pull the oil pan? Will the compression numbers improve with time? I assume they will only drop as it wears.

I had a few issues at the first several minutes of the breakin run causing big jumps up and down in the rpm but no other issues during the build and breaking run.

The engine seems to start easily and run ok.

Thanks