With a 1st time engine builder, I have to wonder if the #4 main that spun was incorrectly installed. If the lock tabs were not in the grooves, the clearance at the bottom may have been OK, but the sides could have been very tight, causing the shells to spin as soon as the heat came up. The bearing shells could have begun spinning on start up, and it took 4 minutes to create enough heat to lock the motor. You are all assuming the new builder had the bearings correctly located.

If the #4 main bearing spun bad enough to lock the motor and turn the cap blue, and the other bearings look OK, how are you ever going to determine the real cause other then to point to #4 spun bearing and its blue cap? Gene