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

[J-Ville VR-4]

Originally Posted by Fury

^ditto, i'll be buying a new oil pump and putting in new rod bearings..curious if its worth shimming up the pump to get better oil pressure?

If I could do it all over again, I'd throw in 1 washer to shim it. I replaced my rod/main/thrust bearings and oil pump all at once, (all the bearings were in good shape considering the 180,000 miles on them), and oil pressure only went up by maybe 5psi at idle, if that. On completely cold starts on cold days, I see ~70psi. If I rev it over~2500rpms, then the oil pressure rises above 70psi. I've probably never revved the car over 4,000 on a cold engine, but I've also never seen my oil pressure go over 100psi. At ~3500rpms it is close to being there, I'm sure if I revved it a little higher it would go over 100.

Anyways my point was, I never have to worry about high oil pressure. I think adding 1 shim is worth it - it shouldnt affect cold oil pressure enough to have to worry about it, and it might possibly help oil pressure at hot idle, which is basically the point of diong this.

I'm too lazy to drop my pan and add a shim in there. I'll do it the next time I have some other good reason to pull the pan off.

[zba857]

so whats the verdict? how much does it raise idle pressure? hot/cold #'s?

[Kriscerosaurus]

Hell, I just want a pressure gauge with NUMBERS on it....I'm not liking watching my needle drop and wondering, "Y'know...what exactly IS that little tick mark there?"

[iGoRa]

So anybody have tested it? or its still in the air?
Numbers?

[tokaygecko]

Don't know if there are any numbers to support it but this mod has been done for the past 8+ years so I know it works. I've done it to every single 3/S I've done major engine work on and they are still run great to this day.

I have no idea how much it raises oil pressure, but I usually shim with 2 small washers and it seems oil pressure goes up about 1-2 tick marks across the board...

[Ondontii]

One of the theories behind this mod is that sometimes our pumps have no tension on the relief so it leaks at idle.


I just added 1/8" of shim (forgot that I only used 1/16" before on a NEW pump) on a 200k mile pump and well, horrible idea. There must be a lot of clearance between the gears and the pump case because along with some sorta thick oil (junk oil and some lucas because of a different oil leak) the motor now runs 100psi oil pressure cold idle (1200ish rpms idle, big cams) and oil comes right out the front main seal. Checked this by removing the pully etc and watching it leak from behind the crank gear.


As Adam said, bad bad idea on old pump. 184 dollars for a new diamante pump, double what I paid for this motor.