In Reply to: The mighty 318 posted by Island Mike on January 14, 2023 at 20:51:11:
If you did the oil addition on a warm engine, That is to say run more than 20 minutes to achieve normal operational temp, Then gaining 25PSI on a cylinder with a wet test is a fair indication a ring job is not too far away.
Dry comp check of 135 to 150 is within an acceptable number, generally no more than a 20 PSI difference.
18 inches of vacuum is a good number and the minor fluctuation should not be an issue.
Since you like playing, grab a tachometer and a pair of nylon pliers used for pulling fuses out of a household fuse box. Nicely insulated to work with.
With the engine running, pull one wire at a time with the pliers.
Note the cylinder that has the lowest RPM drop when pulling the wire.
Two cylinders drop? Firing order is what? Crossed a wire or two?
Now if you have a fair comp gauge set, you can pull the shraeder valve out of the hose, spin that cylinder to TDC compression, and do a leak down check with compressed air. Hissing noise in the oil fill is bad rings, from the carb is a bad intake valve and exhaust noise is a bad exhaust valve.
My money is noise from the exhaust valve but with that 135/160 increase, that cylinder might should be making noise out the carb throat.
Engine pro? No. Just a lucky guesser.