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Original Message
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| RE: Yet another question, (on oil pumps) |
| By John - 05/09/2002 4:53:12 PM; IP 142.177.9.71 |
| Gerry is right...sort of. The only difference between a high volume pump and a high volume/high pressure pump is the peak oil pressure as controlled by the internal bypass spring. I get just under 80 psi max with the engine at idle or above with cold oil, or at 2K and above when hot. The max pressure should be controlled by the spring, but pressure is built up by the resistance to flow in the engine itself. So if you have a loose engine (large bearing clearances), a high volume pump could start bypassing due to the oil gallery restrictions, but with insufficient oil flow at the bearings. A high volume/high pressure pump would cure this. Remember, the pressure you read is at the entrance to the engine from the filter, not at the bearings. It's at the bearings where you want to maintain sufficient oil flow. Typical clearances for a street performance engine are 0.0025". A high volume pump only, will work just fine here. In a solid lifter engine, a stock pump would work fine. A high pressure pump would work for either much larger clearances , which arn't recommended, or at very high RPM's which isn't recommended either (you need a little more pressure to overcome the cavitation where the crank bearing saddle oil holes meet the crank, and where the crank oil holes meet the rod bearings) |
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This thread, so far...
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