OP
You guys scared me. We got the head off last night. Inside the engine (pistons, cylinders) looks impeccable - just a little carbon which we'll clean up. 142K and we can still see the cross hatching on the cylinder walls and virtually no wear ridge. We flip the head over and stare at the valves for a while and panic because they LOOKED fine. I pour acetone into the combustion chamber and around the valves, and boom... within a few seconds, it's dripping down the valve and out the exhaust port. Nothing horribly bad but definitely not sealing correctly. I think that explains why our compression test was OK but not the leak down. So, it looks like a leaky valve is the issue. Waiting on a new head from clearwater and we'll see for sure.