Engine bearing quality and crankshaft finish is technology that has been understood for well over 40 years now. We used to supply GM with Main and Rod bearings for many years. I have seen the process from design to testing. At least up till 2019 when I left as the company was bought out. Maybe the new owners let the true engineers go??? Maybe the new owners decided it was cheaper to bring in bearings from China, manufacturing was split between the USA/ Michigan and Mexico when I left.
GM claims the crankshaft finish was less than perfect and that could certainly cause issues, maybe GM relaxed crankshaft finish so they could build new cranks 5% faster? Maybe they went off shore for bearings and the new supplier did not have the technology needed to make functional parts?
Hard to say without getting actual engineers that have the knowledge to look at the bad parts. The parts will tell the story. I have looked at thousands of failed engine bearings in 40 years. Sometimes a microscope was needed and small particles could be retrieved from the used parts. Those particles could be examined and determined exactly where in the engine the particles originated. It is not magic. How to determine the cause is a well documented process. At least it always was up until 2019 when I was last aware of process used.
In the old days once the parts were designed before GM would accept them as a production run actual dynometer tests were done on multiple running engines and they were put under thousands of hours of testing to see when and how they failed. They were exposed to low octane fuel to watch how they held up under detonation, exposed to high RPM tests, put in severe driving tests, tested with perfect oil and less than perfect oil. Everything was known and proven before GM accepted the design.
Ford insisted on a 300 hour wide open throttle test on new piston designs! That was over 12 days wide open throttle with the engine at max HP RPM on the dyno, if max hp was at 5600 RPM it would run there wide open throttle for over 12 days to meet the 300 hour test. There were about 8 dynomometer's in the bearing lab, 26 dynomometers in the piston ring lab, more in the piston lab, many more at the gasket lab These demanding tests were used to test many parts, everything from spark plugs, water pumps, injection systems, gaskets, bearings, rings, pistons. Everything had to work to run the engine under heavy loads for extreme testing.
I remember the engineers even introducing nitros to engines to determine failure points if an engine did not fail in normal testing.
I understand computers have taken over much of the actual testing and when done right all is still well. GM dropped the ball with these 6.2L engines, to continue building engines with these bearing problems over a few years is absolute negligence. They ignored the problem hoping it would only affect a smaller number of engines. All parts we supplied had to have identifiers stamped on them. You could pick up a used part and know what plant built it, what day, month and year it was built and what shift built the part that day. If there were problems you could trace it back and determine what went wrong on that specific day. In manufacturing parts were checked multiple times before shipping, visual inspections and electronic inspections were done. Core samples were taken to verify the metallurgy on schedule during production. The ball was dropped at GM or standards were relaxed causing this issue.
The engineering department at GM knew the cause and made it known to corporate GM management long before the public heard anything. GM gambled most of the engines would get out of warranty and lost. Now they are trying to present a positive spin to keep customers. OK, I feel better after sharing what little I know about engine parts supply and manufacture, keep in mind my information is going obsolete since I have not been involved at all since 2019. I would still trust the replacement engines. No way would they not fix the actual issue before shipping more engines. ( they might use up the existing inventory first but newly produced engines will be good ). We have not read of any supplier being blamed (yet) which says it was not the bearings fault they are failing.
