Morris Minor Owners Club

Just a word of caution, on my recently rebuilt 1275cc Midget engine it has the usual few drips from the rear inspite of spending a long time making sure everything was ok, and something just didn't seem quite right after a couple of hundred miles so just decided to check the oil presure with an external guage as I dont have one fitted and guess what over 45lbs at tickover and 100lbs under load.
Well one of the improvements carried out was to fit one of the improved minspares type with the shorter spring and ball instead of the original spring and bullet type so I got a new original type and fitted that (what a horrible job that is with the engine in place) and the pressure came down to 35lbs at tickover and 65lbs under load which was far more acceptable and also stopped the oil drip which was not surprising with the original pressures.
On looking at the ball type and spring compared to the original type the spring has thicker coils and on talking to people in the mini tuning side of things they use the ball type for their event cars where the pressure can drop while under competion conditions with the standard setup.
So personally if you are rebuilding an engine stick with the standard relief valve setup otherwise you may have more oil leaks than expected.

100lbs at high revs - that is also not ok. Was this with engine at full temperature on both tests?
if the pressure is lower at tickover with one valve, but conditions were the same, then the relief valve is leaking!
A valve leaking even when at low pressure is probably more serious than the 100psi.