rogueinla

Working on a friend's 1987 Pickup with 22R motor. Seems to have excessive pressure under the valve cover. There's oil on top of the valve cover around the hose going from the v/c to the air cleaner, and the inside of the carb is black, not from soot, but from oil. Checked compression, 150/135/135/150, so that seems ok, did a leakdown test, leakage is less than 20% on all cylinders (well within the 'low' scale on the leakdown tester). PCV valve seems ok, when I pull it and put my thumb over it, it's definitely pulling vacuum. Going to change it to see what happens. I don't believe this would be valve seals, as they typically let oil leak into the cylinders while sitting, correct? In any case, the leakdown test gave no indication of any leakage out the valves, or rings. Remove the oil cap and there is a LOT of pressure there. I've read here in the forums that can be caused by a bad ring, but again, good compression and very low leakdown indicates that isn't the problem. Has anyone dealt with this issue?

Thanks in advance for any help.

rogueinla

Update, checked and cleaned the baffles under the valve cover, replaced PCV valve, adjusted valves, removed the carb and cleaned the vacuum passage under the gasket/spacer. Still have pressure inside the valve cover. Having run the motor for awhile (it had been sitting) the compression is now 155/150/150/160. However, which I find odd, there's no pressure coming out the dipstick, as the motor isn't separated into valve cover/crankcase, but are open to each other, if there's pressure on top, there should be pressure on the bottom, or have they changed the laws of physics when I wasn't looking? Anyone have any thoughts on this, or experience with this type of issue?