Conclusion: My own fault.
With the help of a friend who knows these engine quite well we talked about where the oil could have gone and were able to piece together a quart here and a quart there, finally coming close to the 3 quarts missing from the engine.
In all the confusion of trying to get the engine running for the first time I did not replenish the oil that escaped from some of the repairs - replacing the oil filter housing, installing a second filter thinking the first one was bad, etc.
The lack of oil in the pan, plus the fact that the bottom of the pan was severely dented and pushing against the pickup, explains most, if not all, of my issues. The immediate 50 lbs of pressure that quickly dropped off to near zero pounds. The air in the gauge line.
Though I constantly checked the dipstick, which showed adequate oil in the pan, I failed to realize it was giving me a false reading. It was purchased as an exact replacement for the engine so I trusted the reading was correct. It was not. It was reading from a small amount of oil in the front of the pan, which I learned when I dropped the pan. With the pan out I was also able to tap it back into shape giving the proper clearance for the pickup.
This has taught me a valuable lesson. Slow down. Double check everything and trust (the vendor) but verify.
The upside is (along with being taken off suicide watch), I now know the pump and pickup are fine and properly installed. And with all your help I've learned quite a bit about this engine and its oiling system.
Buttoned everything up yesterday and now have a steady 70 lbs of pressure while priming, which I believe will go down some as the engine breaks in.
Thanks to all here who gave of their time and knowledge. So greatly appreciated.
Patients is a virtue. I would be all over my motor guy and have him come take a look. LOL.
