What I do before I start on an engine repair is install shop air into the cylinder when the piston is up and the valves are closed, compression/power stroke. That gives you a heads up on where the compression is being lost,
It is called a cylinder leak down test, I add full shop air and if the air comes out the oil filler it is a ring problem, if it comes out the intake it is an intake valve problem, if it comes out the exhaust it is the exhaust valve, then you have to figure is it just the valves are to tight or what. I cuts down on unnecessary repairs, and misdiagnosis.
Just a thought!