Damn Oil!!

[Monstertrucker]

Compression loss is usually due to poorly seating valves. As with the stem seals, it's the exhaust's that wear the most because of the heat that they're subjected to.

If you just have the heads rebuilt, (all gaskets and stem seals replaced and a fresh valve grind/hone), you'd be back to good as new.

Piston rings are the last thing that will cause poor compression, given the beating that the valvetrain gets and the size of the components/sealing materials used.

[Ebenezr]

Compression loss is usually due to poorly seating valves. As with the stem seals, it's the exhaust's that wear the most because of the heat that they're subjected to.

If you just have the heads rebuilt, (all gaskets and stem seals replaced and a fresh valve grind/hone), you'd be back to good as new.

Piston rings are the last thing that will cause poor compression, given the beating that the valvetrain gets and the size of the components/sealing materials used.

I almost pulled my heads to do a valve job but my mechanic had a method of pumping compressed air into the cylinders with the valves closed. He said if the valves were leaky then there would be an audible hiss. In my case he decided worn rings was the culprit. Years ago it was sort of a risk to do valves and not the rings as well because the firmly seating valves increased compression and worn rings allowed "more" blowby. Therefore doing a valve job only kinda didn't work well.