I agree with Dodge Trucker. Were the oil passages flushed before assembly? By you? I find it strange that just one bearing gave a problem.
Back in the sixties a Buddy had a 55 Chevy 210 that would take out #2 main on the crankshaft after leaving the lights. Took a bit to figure out what was causing it because the engine had a high volume oil pump. The second time we not only examined the oil passages but used a piece of wire and low pressure air and checked all the oil passages on the crank. Sure enough a small piece of light brown paper came out of one passage. Next we cut the oil filter apart and the filter element had ruptured sending pieces of paper into the oil passages. This was one of Andy Granatelli's STP filters. After going to another brand of filter we never had a problem again.
What did the crankshaft look like?
Back in the sixties a Buddy had a 55 Chevy 210 that would take out #2 main on the crankshaft after leaving the lights. Took a bit to figure out what was causing it because the engine had a high volume oil pump. The second time we not only examined the oil passages but used a piece of wire and low pressure air and checked all the oil passages on the crank. Sure enough a small piece of light brown paper came out of one passage. Next we cut the oil filter apart and the filter element had ruptured sending pieces of paper into the oil passages. This was one of Andy Granatelli's STP filters. After going to another brand of filter we never had a problem again.
What did the crankshaft look like?