L78steve

Relief valve plug - 96041864

Tom Oost

Wondering if you were able to verify that pan relief being the issue. I have a 6.2 fresh rebuilt with 15 psi hot oil pressure. Mobil 1 filter and 5-w30 oil. New bearings, cut crank. Plasti-gauged clearances and they are all to go spec. New Melling pump also. Cold oil pressure is good. 50-60 psi. All verified with a mechanical gauge...

thanks,

Tom

tjoyce81

iTrader: (1)

Here are my recent experiences with the AFM/DOD pan relief - 2007 LMG VIN 0 motor. I had oil pressure that fell from 40psi to 7psi after a short warms...Changed everything in the system EXCEPT the pan relief valve. After I studied the way the relief valve works - I decided just delete it...BECAUSE, when the valve is doing it's job - it dumps UNFILTERED oil back into the pan... I proved this to myself when I took the pan down (for the second time in a week) and noticed LOTS of actual dirt in the pan. I then cut open the NEW filter with NEW oil in it, and it looked like a filter with 20000 miles on it - unbelievably dirty. The reason I was alarmed is because the oil and filter only had about 1/4 (one quarter) of a mile on it - and about 20 minutes or so of running time...After such a short period of running time, and the fact that when I plugged the relief valve the oil pressure went back up and the oil in the pan matched the filter condition, I believe that plugging the AFM/DOD relief valve in the pan is the right thing to do.... I should add that when I removed the pan the first time, I made sure it was spotless when it was installed.
Here are the pics of the mechanical oil pressure differences before and after the delete. The top gauge is hooked up in place of the pressure sending unit, and the bottom gauge is hooked up at the oil filter area. This insures that I have the pan relief valve in between the gauges.

before delete
BTW -- this engine has 287000 miles on it.
after delete

john john

[QUOTE=rsz288;12134481]The primary purpose of the pressure relief valve in the oil pan is with DOD/AFM engines with higher volume oil pumps to support the DOD/AFM oil usage and probably also with VVT.

With 30% higher flow in these cold start oil pressure (sub zero locations) can be through the roof and exceed the specs of the DOD/AFM solenoid valves which it appears maxes out just north of 75psi.

In non DOD/AFM engines, they may bleed some pressure off even with the stock oil pump if the engine is tight oil wise.

If you have 50psi hot and want to chase the "rule of thumb" 65psi at 6500rpm (which is way above GM specs, but then GM specs arent for racing ), then maybe you will get there by blocking the relief off. You may also get 100psi and be driving the oil pump real hard and taking more power that is unnecessary, and possibly heat the oil up further than normal. And if the DOD/AFM solenoids are still there, well, maybe they will give up.

GM put the relief in there for a reason. If you have 55-65psi hot (like 210-220 hot), then you probably dont need to worry about any more pressure.

[ i agree with your logic. I have an L76 and am going install an oil pressure relif valve deflector as chev installed these deflectors on later models. The original version sprayed oil on the cylinder walls and increased oil consumption. In 2010, GM added a deflector (p/n) NAL-12639759 to redirect in into the pan. This should be added to your earlier model if you experience oil consumption.
Engines with AFM also use a special camshaft, a high-volume oil pump, and a pressure relief valve in the oil pan.
also if deleting the DOD It is also recommended that you switch to a standard-volume oil pump as an the high vume oil pump could more regularly open the relief.
hope that helps