2.2 crankshaft problems

I have a nice '91 b2200 I bought that was smoking pretty bad because of stuck rings,I pulled the motor for a standard rebuild,the block sleeves was very good and the crankshaft only needed a little polishing.I had the head rebuilt,the block cooked out,used sealed power rings and clevite bearings,felpro gaskets and a melling oil pump..After 12000 miles of running perfect the oil light flickered at idle so I checked the oil pressure to find it very low.I pulled the oil pan to find the no. 3 main bearing side surface to prevent end play completely wore away and the crank scored up on the transmission side,any ideas why this happened?

Idk on engine rebuilds but I would pm axel breaker earl on here he can better answer this bc he rebuilds engines and espec the bseries.My guess is crank bearing caps not torqued correctly or seated right.We had a guy on mazda truckin with a tap knock sound and wore a bearing bc of left it loose or did not torque correct.I am not a engine guy but,axel breaker earl knows these internals pretty good and could assist you better.Pm him hope this helps.

hello b brothers and sisters.