FWIW I have never been able to accept that the crude Healey (all BMC
for that matter) 'pressure relief' valve, opens and closes that many
times per second to manage the oil pressure we see at the gauge. The
seat and valve are too poor a fit to be a positive seal and it does not
remain shut until a certain pressure is reached. The volume of oil that
flows thro a restriction, ie bearings and spray holes etc varies with
tempreture, engine speed and general condition and bearing clearences.
May I suggest that our 'relief valves' are flow control valves and apart
from when the engine is stopped, the valve is never in the closed
position and thus providing a positive shut-off. The spring/valve
manages pressure by controlling the volume of oil allowed to by-pass
into the sump.If you inspect a valve it usually is a loose fit in the
bore and shows signs of having wear on opposite sides at the two ends,
an indication that it spends most of its life rocking back and foward in
its bore. Usually most of the oil supplied from the pump should be far
in excess of the volume that can circulate thro the engine and therefore
is continuously being by-passed back into the sump (pan).
Most hydraulic system start-ups require ALL air to be bled before
commissioning.
Therefore it is most likely the weak spring tension that is allowing too
much oil to by-pass when pressures are insufficient with the engine in
GOOD condition.
I drove my BN.4 on my honeymoon with 15 psi on cold start up, 12 psi hot
and used it as an every day work transport from Dec. to April when a
re-build was in order.
Are there any hydraulic engineers out there? I am just a simple working
man.
Joe
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