Tell me this noise isn't what I'm afraid it is.

[Ross F-1]

Originally Posted by Old Henry

Compression spec in the operator's manual is 105-125 at sea level which translates to 70-83 psi at 5,000 feet where I live which all but in is within so the overall compression is OK, especially since no one cylinder varies drastically.

Correct, on a fresh rebuilt 8BA at 5350', I get 85 - 90 psi across the board (heads have not been shaved).

I wouldn't dream of running that engine until the oil passages and sludge traps had been cleaned out, in addition to whatever the crank/rods need. Pulling the engine is not that big a deal, you can have it out and on the stand in a day. I always have a lot of inertia, trying to figure a way around it, but in the end it's better to just bite the bullet.