Oil Pressure Drop

[Ol' CW]

Another thread made me think of this

On my 383 I have a Z28 high pressure pump. When cold this gives me around 55 psi. Once the engine gets warm, this drops a lot, down to maybe 5 pounds at idle. I have had the same experience with 10-w30 conventional, 15W40 Amsoil Diesel oil and now with 20w50 Amsoil racing oil. As soon as you give it gas it hops back up to 30 psi

I even added a washer under the pump spring and noticed no difference. Does anyone else have this problem? I think maybe it has something to do with a little extra side cleaerance on the Eagle rods(can't remember exactly what it was now, been a while), but this was a factory rotating assembly

Engine has many hours on it now, never any shavings out of the ordinary in the oil. Just kind of annoying.

[Ol' CW]

BTW, pan is a 6 quart Moroso which I usually put 5.5 quarts in and I run the long GM truck filter (almost 2 quarts)

Thermostat is a 160 and coolant never gets much above 190 even when you stay in it a while

Also tried one of those sandwich oil cooler adapters with a B & M stack plate cooler, it made no difference so I took it off for simplicity's sake

[Norris]

Your engine is leaking more oil past the bearings than the pump can build pressure for at low rpm. The bypass valve and related spring only control the highest pressure. Smokey said it takes 10lbs per 1000 rpm, so your a little too low. The right way to fix it is overhaul the bottom end, a bandaid would be to put an HV or even a bigblock pump in it. BOth produce more volume and could overcome the severe leakage.

[MCEcomp]

Side clearance has nothing to do with it... I ve run eagle rods with .032 side clearance.

Look at verticle oil clearance on mains,pins and cam bearings also check lifter bore clearance.

[L89 chevelle]

Originally Posted by MCEcomp

Side clearance has nothing to do with it... I ve run eagle rods with .032 side clearance.

Look at verticle oil clearance on mains,pins and cam bearings also check lifter bore clearance.

I will ad another, make sure the mating surface between the oil pump and rear main are also flat. They leak alot there also.

[Ol' CW]

Ahhhhhhh, never thought of that.

Dodge uses a thin gasket there, wonder if I could get away with doing that to a Chevy

[BlackCat13]

Originally Posted by Norris

Smokey said it takes 10lbs per 1000 rpm, so your a little too low.
.

Didn't he also say to take the pressure reading at the FAR END of the system, not by the oil filter?