The early Chevy and Pontiac 2.8L V6 had a similar problem with burning rod bearings near the center of the crankshaft. I found that when the oil passages in the block were drilled from each end when the blocks were machined, they didn't quite intersect- - - -creating an oil flow restriction at the center main bearing that resulted in the rods pressurized from the center main to be starved for lubrication. We made up a long drill bit to chase out the oil galleries when we rebuilt those engines.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!