Russ,
90 PSI? I thought the relief opened at around 55 PSI?
My (original 1962 BMC) shop manual reads: "Oil is passed to the filter from
the pump at a pressure controlled at 50/55 lb. per sq. inch by the engine
oil relief valve."
It further states that the free length of the spring (always 13 coils, and
.484" OD) is 2.562" on the earliest BN4s, but 2.687" on cars with the 6-port
head, and later. That would seem to indicate that the pressure would be a
tad higher on the later cars.
It is interesting to note that 20PSI is considered normal for idling, with
only 50PSI expected at 40MPH (gear not noted).
Dick Hosmer
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