Laughinq_Man

Ok, my car is a 90 Lx 5.0. When I bought the car, the engine had terrible oil pressure, like 4 or 5 psi at warm idle. The stock gauge of course read that the pressure was fine until it hit 4 or so, then it would bottom out. I rebuilt the bottom end- ground the crank, new bearings, oil pump, oil pump shaft, etc. Checked the pressure with a mechanical gauge, got 50-55 psi on the new build.

The car runs great now, no clatter from the lifters, way more power, can actually idle. My problem is this. I've put less than 50 miles on the car since the rebuild and suddenly the stock gauge is bottoming out again. If the car is sitting idling, every now and then, the idle will drop just a little - I think a sensor or something is bad. When the idle drops, the gauge will drop to zero, but the engine never makes any of the noises associated with the pressure dropping.

I'm thinking it's just a problem with the stock gauge, which I plan to replace with a mechanical one soon, but I'm not totally sure. All the bearing clearances were within spec when I rebuilt the engine, and it runs quieter and smoother than it ever did before - haven't heard a single tick from the lifters. I'm mostly just looking for suggestions to consider until I have the time to put the mechanical gauge in and see if my pressure really is fluctuating that much.

Gronk72

Mechanical gauge is the only way to be sure.

FivePointOhh

dont even look at that stock gauge. get an aftermarket mechanical gauge and verify pressure off that before you suspect a problem. stock guage, a.k.a. "dummy" gauges

Laughinq_Man

That's what I've heard. Last time the stock started going nuts, there was a problem, but it was something that a mechanical would have shown quite a while earlier. I'm hoping this is just another problem with the gauge. The engine is a fresh build and isn't giving any of the signs of being oil starved so hopefully the mechanical gauge will tell me good things when I get one in a few weeks.
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GT350

I would bet you put some kind of sealant on the extension tube or the sending units threads. The gauge works by being grounded to the block, the sealer will prevent the grounding to the block, take it apart and check for anything plugging the sending unit and put it and the extension back together with nothing on the threads.