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Actually in the engines I have ever rebuilt, I always paid strict attention to the oil pump... (the heart of the enging) Like all "precision" assemplies, oil pumps have their "tolerances" too. Oil pressure is lost if the gear/cover clearance is too much. This is because oil is being forced, in volume, by the teeth or rotor of the pump. It cant develop as good a hydraulic vacume, to draw oil (when air can slide by), at the rate it should. Same token on the gear backlash. The correct backlash gives greater oil moving capacity. It can create better vacume if there is a tighter clearance. So in a way you can say gears can make pressure and gear/cover clearance can take it away. I dont know what the specs are for the sa pump but in air cooled continental aircraft engines and alike, Porsche, etc., its quite small. Usually arouund .0015 and less and al little more for the teeth clearance. Get some numbers and check it over if you want it as good as posible. scott#2 Just my half cracked view. PS Ive even gone as far as swapping different pump cofigurations out on test engines and have documented results in this area. And I will say this. Very rarely have i received a new pump that wasnt as good as it should have been. Alot arent even at the spec that the manufacturer states. Sometimes they are worse to straighten out than old ones.
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