With the new water pump installed, the AC compressor pulley was still not aligned with the water pump. The AC pulley was about 1/8" too far forward, causing the rear most edge of the fan blades to contact the front of the AC compressor clutch hub. Luckily, the compressor is mounted to a slotted adapter plate that is bolted to the compressor mounting bracket on the top of the cylinder head.
I slid the compressor rearward on the plate to align the pulleys and eliminate the contact point between the fan and the compressor clutch.
Success!
I verified there was clearance between all the rotating parts, filled the cooling system and hooked up the battery for an initial start with the new pump. I cranked the engine over with the ignition off, just to make sure there were no major surprises. All good!
I turned on the key and hit the starter button. As soon as the engine started, there was a terrible loud metal-to-metal knocking noise. It sounded like a jackhammer. I shut it down immediately and started looking for the interference.
I saw nothing obvious, but I verified that every blade of the fan was clear of the compressor hub, and also verified there were no other potential points of contact with the crankshaft balancer or any other parts. When I was certain that everything looked clear, I tried it again, with the same results. Sorry, there's no video of this; I was too worried about it to let it run long enough to record a video.
I thought perhaps the compressor was damaged, so I removed the AC drive belt and tried it again...no improvement.
Then I removed the water pump & generator drive belt, assuming that I got a bad water pump. Started it again;still the same horrific noise.
By now, some of you might have guessed what happened.
When I raised the engine to provide room to install the new motor mount bushings, I dented the oil pan. Obviouly, a 6" long piece of 2X4 was not an appropriate saddle for that task.
I dropped the oil pan about 1 inch and ran the engine for a couple of seconds - no jackhammer noises!
It looks like 3 crankshaft counterweights were hitting the oil pan. When I got it off the car, the witness marks were obvious:
The good news is the oil pan was fairly clean. There was about 1/4" of sludge in the sump area, but there were no metal shavings or "glitter" in the oil.
I cleaned the pan and hammered out the dented area. Once it's painted and reinstalled, I should be ready for a test drive...once the front seat is finished, of course.