My 74 350 2bbl has low oil pressure, 40 psi when cold, 5psi when warmed up at idle. When cruising at 55 mph, the oil pressure will jump up 10 to 20 psi when you let off the gas. This motor came with my car, and was bought from a wrecking yard by the previous owner. Somewhere along the line a high volume pump was added. There is wear in the oil pump housing, so I know this is part of the problem, but what makes the pressure "spike" when you let off the gas? Thanks
