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Oil pump shim

I shimed my 5mgte oil pump about 1/8" ,back in 1987(40,000 miles on motor never been rebuilt since),pressure at idle is 16 to 22 and never goes beyond 65 psi. normal driving :wink: is usually 35 to 50.Thats using 15/50 synthetic oil.
 

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I placed washer on relief plug it doesn't have to an exact fit,this will not cure low oil pressure at idle,will only increase your max oil relief pressure.
In a high mileage engine, low oil pressure is often due to a combination of worn main and rod bearings and crankshaft journals. The oil pump itself does not create pressure. It produces flow and the resistance to that flow produces pressure. Resistance is created by the orifices in the engine block through which the oil flows, and the amount of clearance between the bearings and crankshaft journals. As the bearings wear, clearances increase allowing increased flow which reduces pressure.

The pressure relief valve, located on the pump body can be yet another cause of low oil pressure if the valve sticks open or is held open by a small piece of debris. The relief valve is designed to limit oil pressure as engine speed increases. The valve opens when pressure reaches a preset value (typically 40 to 60 psi). This vents oil back into the crankcase and limits maximum oil pressure in the engine. The reason for doing so is to prevent oil pressure from reaching dangerous levels. Too much oil pressure can be just as bad as too little because excessive pressure can rupture the oil filter or even blow out pressed-in oil galley plugs in the block.
 
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