Re: 80 lb oil pump in 1935 flathead - is this okay?
The original relief spring was designed to relieve the pressure at 50 psi. They went to an 80 lb spring in 1941 when Ford changed the rear crank seal arrangement from the slinger type to the rope seal type. If the fresh rebuild kept the slinger rear seal, the motor should stay with the 50 lb relief spring. You MIGHT have oil leaking out the back if the pressure is 80 psi and the crank still has the slinger type rear seal. This is easily resolved by changing the relief spring from the 80 lb to the 50 lb spring.
As stated above, the oil pressure will relieve at the point of least resistance, so even if the oil pump (ie 8BA type) has the normal 80 psi relief built into it, the system will relieve at 50 psi if you’ve got the 50 lb spring installed. Both type springs are available.
If the block is the 49-53 type, it is only designed with the rear rope seal (no slinger) so the 80 psi 8BA oil pump will keep the maximum relief at 80 psi. Those blocks never had the pressure relief plug and spring in the oil galley tube, so the relief spring only exists in the pump itself. The 49-53 motors are very content with the 80 psi system.
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