Don---55 lb. of oil pressure at 3,000 rpm is a little low, but not worth
a lot of concern. 40 lb. when idling on a hot engine is high, so there
you are! These two readings are in conflict, so there's a missing piece
here somewhere, and it isn't a thrust washer. (Thrust washers do nothing
for oil pressure, as they do no more than keep the crank shaft from
moving forward or back.) If you hear no strange new noises coming from
the engine, consider changing the oil, if it's time. Old oil can
sometimes be diluted with fuel, causing pressure drop, but this would
also show up with the engine idling.
Lastly, many think because an engine reaches operating (water)
temperatures of 180 degrees or so that the engine oil is at its thinnest
viscosity, and report oil pressures that are high. Long runs of an hour
or more on a hot day at over 3000 rpm will nearly always bring even the
tightest engine's oil pressure down. 15 lb. at idle and 70 at speed
would be normal for me. (When using 20W 50)
Dick T.
'73
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