Ok, so here's the deal. A 1971 Karmann Ghia came into the shop because of loss of oil pressure. Someone spent some money, because this was a very recent rebuild, and looks to have a few parts thrown at it. Originally a 1600, but now has a big bore kit, twin carbs, and a bunch of extra stuff that's not important right now.
We pulled the engine and cracked it apart, and were horrified by the amount of silicone inside the motor. also it did not have a screen on the pick-up, so it all went through the pump, and all through the oil galleries. To make things worse, this motor has an oil pan extension, and someone must have left a rag inside it during assembly, because it was crammed up the oil pick-up tube.
At this point the problem is obvious. I mean, of course there's no pressure.. no oil could possibly get through!
Everything came apart, and everything got flushed out. Crank and rods were ok, so a new set of bearings and everything else involved, and it's back together. So far so good.
Motors is back in the car, all hooked up, ready to go. We fire it up, and oil pressure is low, but slowly climbs to over 50psi. Still cold at this point, so it's expected. Thought there could be some air in the system somewhere, so starting at low pressure wasn't unexpected. Figured we should let the car get up to temperature, so we let it run. Then the pressure hits rock bottom, barely registering on the gauge. Not good, so car gets shut off.
Seemed pretty sudden, so the first thought was wiring, or the sender. Put a mechanical gauge on it, still nothing. The new gauge hadn't been used for awhile, so it's possible it was stuck, but I'm finding it unlikely that two different gauges failed.
Next thought was the pressure relief valves, so they both got pulled. Didn't find anything wrong, they came out like they were supposed to, and couldn't find any debris or anything that might be holding them open. Now that I think about it, it's possible the springs are backwards, didn't think to check at the time, but would that cause 0psi?
Drained the oil, to check for bearing material. Comes out clean.
Checked the pump, no wear, withing spec.
Been reading up on what causes loss of oil pressure on these things, but so far I haven't been able to find anyone with this exact problem. Even if the bearings were fried, and the pump was toast, it should register SOMETHING, especially at high RPM.
Also, the engine hasn't died yet, how long could one of these run with no oil?
At this point I have no idea what to do. It's my first time working on an air cooled VW, and I already hate them.
Please help me.