Engine: Shim Oil Pump for Higher Oil Pressure

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How to shim your oil pump relieve valve for higher oil pressure

I tore apart a spare oil pump yesterday and it is extremely easy to shim the relief valve spring for higher oil pressure, IF you have the oil pan off the car.

The theory is that the relief valve keeps the oil pressure from getting too high at higher RPMS. At lower RPMS the releive valve is supposed to be closed completely. Many people believe the relief valve opens a little at lower RPMS bleeding off a little oil pressure. Shimming the spring increases the oil pressure at higher RPMS but it might also keep oil pressure a little higher at low RPMS.

There are other threads discussing if this actually helps at all, I will link to them later when I find them all.


For now I will just describe HOW to do it.

With the oil pan off the engine, better if pump is off the car) look at the bottom of the oil pump. There is a big (24mm?) bolt head next to the oil pickup tube.

OilPump1.jpg

Remove this big bolt being carefull to catch the spring that will pop out.

OilPump2.jpg OilPump3.jpg

The bolt has a recessed pocket in it that the spring sets into. Drop a washer into this pocket then put the spring on top of the washer and re-install the bolt. Make sure you use thread sealant on the bolt.

Thats it! The thickness of the washer determines how much the oil pressure is raised. When I have some spare time I will measure the spring tension to get an idea of how much the oil pressure will change based on spacer thickness.

I would love to hear from anyone who has actually done this. My engine won't be running for awhile so I have no idea how much effect this will have.

DISCLAIMER: DO THIS AT YOUR OWN RISK! Too high of oil pressure can be just as bad as too low of pressure.

This article originated from a thread or post on 3000GT/Stealth International. (1879)