jackson 63

I replaced my pan gasket on my 1963 340HP 327. Before I closed the eng up I checked my crankshaft endplay. According to my 1963 Corvette manual is states the clearance should be .002 to .006. I have .012, is that OK or if not what can I do about it. The eng was rebuilt about 10000 miles ago.

Westlotorn

Wear on the Thrust Bearing is usually caused by external force on the thrust bearing while running. Usually an Automatic car with a ballooning torque converter.
If you have/had a bad set up on your throw out bearing putting pressure on the thrust it may have caused some wear but your throw out bearing would have failed also. It takes a lot of force to make a thrust bearing wear.
Old school thrust bearings could run with 350 to 400 pounds constant load and not fail. Newer designed ramp and flat Federal Mogul thrust bearings can triple that load and not fail.
If your pan is still off pull the rear main and look at the thrust bearing to see if it is wearing or was just built loose. I assume you have had no issues with knocking?

rongold

Rear main bearings are available with oversized thrust faces--I have one in my 435/427. The thrust flange on the crank I got was worn, so the crankshaft grinder refaced it, redid all the journals, and supplied me with a 10 under, 20 over rear main bearing (10 under for the journal, and 20 over for the thrust flange). The end play then came in within spec.