Ok here we go with what i have. 59AB basic stock engine. Its in a truck I got 1-1/2 years ago. have 0 history on engine. Runs really well. It has always carried what seamed to be high oil pressure for flathead from what i have read. 60-70lbs cold then 45-50 warm at idle. It has no oil filteri removed it. All at once small autometer electic pressure gauge reads 0 at idle warm or cold. At 800-1000 rpm gaige goes to 60-70lbs and maintainsa pressure at that rpm. engine idles at 500rpm.I installed the gauge new when got truck. I have had small cheap mechanical pressure gauge hooked in at filter supply port every since i removed the filter when first got truck just to keep eye on pressure when uder the hood. It has always read really close to the electric gauge in cab. Now when the gauge in cab reads 0 the one under hood reads 5-20 with very quick bouncing needle can even feel pulsing in plastic feed line if hold in hand. Im not sure wich way to head to check this out. I pulled intake and checked out the relief valve under intake. It was clean and seamed to have no issues. Can some one explain to me how the relief valve under intake works along with the valve in the oil pump. When had intake off the valley looks really clean no sludge or grim what so ever. It has adjustable lifters with standartd mushroom valves. So somework has been done on engine but not sure what or when. Thanks for any input and guidance.
One reason for that relief valve under the intake is to supply some oil to the stock water pumps. The early water pumps 1948 and earlier including the 59A have bushing supporting the pulley shaft. The end of the plunger under that relief spring has a flat side which always allows a small amount of oil to get into the area behind the timing gear. This now allowed oil to get to the water pump bushings by the windage of this oil. Very early oil pumps did not have a relief valve so this forward valve also took care of that issue as well. Todays replacement water pumps for the 1939 to 1948 engines which includes the 59A now come with bearing's on the water pump shaft. That leaking oil system thus is no longer needed. This oil leak is actually in the main oil artery of the engine so in effect it is a small leak but not a very big amount to effect a loss of much oil pressure. Ronnieroadster
Here’s my guess: If the gauge was previously in the line from the block to the filter, it would have been at the highest pressure because there was a small, pressure building port in the fitting on the side of the canister. You removed that, so now the sender is attached to the large oil galley through the center of the block. Or maybe that’s a bunch of hooey?
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