I did a compression check on my 350 chevy. I have low compression of 175psi on one cylinder.The other seven cylinders range from 195psi to 205psi Could the valves be too tight on the cylinder with 175 psi compression?
Chev engines have hydraulic lifters, keeping the valves adjusted correctly at all times. 20 lbs isn't much to worry about anyway, but if you want dump a little oil (about a tablespoons worth) into that cylinder and recheck it. If the compression jumps up, then your rings are getting weak. If not, you may have a leaky valve.
unless they have been tampered with that wouldn't be it,they usually wont tighten up on their own,i would suspect maybe a valve with a slight burn place on it that's causing that to happen or a ring causing you to loose that much compression,try adding a small amount of oil in the cylinder and then do the compression test again,that will tell you if its a ring or a valve,that's a big loss of compression ,and when you see that much of drop its usually a burnt valve.good luck.
