I have pulled the plug wires one cylinder at a time.....to me no noticable difference in the sound.
I don't have any expierence with damaged engines and the various sounds they give off. We had a stethascope out....lots of interesting noises in a running motor
I am going to go through the complete valve train...I have a hydraulic cam...so I will redo the 0 lash, look for a bent push rod check all the rockers etc. If that doesn't work the intake will come off to check lifters....and then pull the
oil pan and see what I can see.
I don't want the motor to go catastrophic as I would like to save the heads, valves intake etc.etc
John