> It might be worth rigging up a leak down tester to find out where/why the
> compression is low. I've done this (cheaply) by screwing in a plastic hose
(pipe threads on one side, hose barb on the other)
>into the spark
> plug hole. Apply some compressed air with the piston at TDC then listen
> the leak. (be careful the engine doesn't suddenly turn) If you hear
> in the tailpipe, likely the exhaust valve is burned, intake tract = intake
> valve. Hissing from the oil fill opening is bad rings. Evidence of air in
> the cooling system is either a cracked head or blown head gasket.
Okay, I'll bite: What kind of engine uses pipe threads for sparkplugs???
(Besides the Model T Ford, of course.)