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01-03-2008, 09:19 AM   #11 (permalink)
Motorhead
 
Join Date: Jan 2001
Location: Pullman, WA
Posts: 2,449
Re: high voume vs. factory spec oil pump

Attempting to look at this logically (bear with me), your bearing clearances and lifter orifices provide the resistance against flow, while your oil pump can deliver a predetermined amount of flow and pressure. The ONLY way you can flow TOO MUCH oil, and drain the pan, is if

A: the pump provides extremely high PRESSURE AND VOLUME, and pushes way too much oil through the bearings and to the topside of the engine through the lifters, or

B: The pump supplies a normal amount of pressure, but the bearings and/or lifters allow an excessive amount of flow.

In case A, it is clearly the fault of the oil pump, as the bearings and clearances were set up correctly, but excess pressure caused an abnormally high amount of flow. In this case, if a stock type pump, or a HIGH VOLUME (normal pressure) pump were used instead, the pan wouldn't get sucked dry and everyone would be happy

In case B, the pump CAN be a high volume pump, but as long as it has the correct pressure rating on the relief valve, that extra volume should just return right back to the oil pan. However, since there is inadequate oil restriction in the bearings and lifters, they allow that excess flow from the pump, and the pump is happy to oblige. In this case, if a stock type oil pump were used, you wouldn't suck the pan dry, but you would see a definite loss of oil pressure vs. the high volume pump, even though they were both rated at the same pressure.

In both cases, I think you are probably best off with the high volume, standard pressure, oil pump. If you have normal oil pressure (40-60psi) and are able to suck the pan dry, that is caused by other issues, not the pump, and the only way to lower the volume is to also lower the oil pressure which is generally not good a good thing.
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'86 Bronco, 460, E4OD; '85 Ranger, 350hp 289, T5, 12.9@110.5
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