Troubleshooting Head Components

In my first post I mentioned suspecting a couple cyls losing fluid quickly.
With #4 sucking oil as it was, the oil flooding the guide likely causing a tarry substance to be blasted behind the rings every power stroke. The cylinders will be tapered and the rings are likely stuck in their grooves, at min taper, and won't seal.
This is one of those times you hope to be wrong, then experience pops up .
Good luck