Besides all the plugs removed and the throttle open, the choke should be
pulled and (as I learned recently) the engine should be a full operating
temperature so that all metal pieces are expanded to the size they would
be under normal operation. If the cylinders are all low or there are one
or two low (suggesting a leaking head gasket), the next test is a wet
compression test where a few cc of oil is poured into the cylinder through
the spark plug hole before testing. If the pressure is restored, rings are
suspect; if not, the valves. None of my Triumph manuals say much about what can
be learned from a compression test, but the most thorough discussion I have
seen is in my "Classic Car Restorer's Handbook."
Richard Breedon
'74 TVR 2500M
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