I've got an 81' 22r in my 83' 2wd... recently had the bottom end rebuilt but the head was left alone. It's burning oil and I'm assuming it's the valve seals. I could just replace the valve seals. or I have a 20r head from a wrecked 79' 4x4 sitting in my shop. I've never done any internal engine work on a 20/22r so i really don't know what I'm getting myself into either way. I'd be interested to know what someone with more experience would do.
First thing I would do is a leak down test. Make sure it is the seals. Unless they are really really bad, it should smoke mostly during startup and be fine until the next startup. I've never seen a set so bad they caused smoke the whole time.
Smoke is really bad on startup... not noticeable when driving unless i'm pulling away from sitting idling at a light or something. I don't have the tools to do a leakdown test but I did a compression test and got 175 even on all cyls dry and then got 190-205-205-200 wet.
