I got under the car last night and poked around for several hours. The main bearings show fine scratches from metal, but are otherwise OK. Crank journals are not scored or blue. Crank endplay is fine.
Cam lobes & bearings look OK. It was very hard to examine the dist drive gear on the cam, being upside down under a car and all. It looks like the drive faces on the gear teeth have taken some abuse, but I don't know how severe it is. Do I have to pull the cam whenever gear wear is suspected?
I mocked up the pump and distributor and examined how it fit together. It seems that the distributor may be at fault, even though it seems to have the same critical dimensions as the stock distributor.
I may be dealing with a complex issue, where distributor shaft end-play, combined with the block dimension of dist mount to oil pump mount caused this. Why else would this dist work in a '54 engine, and cause a problem in a '60 engine?
Also, does the oil pump body supply any lateral support to the distributor shaft? The stock shaft fits snug in the oil pump, where the HEI shaft only contacts the pump at the drive tang.
ideas? observations? insults?
chip
