[Walt Fricke]

I don't think this is due to corrosion. If it were, I'd think that the main bearings (which show no signs of this) would be affected also.

It has some of the hallmarks of wear, since the dark coating material still exists at the ends of the bearing halves. Checking with bearing wear sites, I see that it is normal for the parting line area to be unaffected by most wear problems.

As best my fingernail can tell, the lighter, more gray areas are depressed below the more silver layer. The silver layer looks like the babbit. Not only is the coating gone, but one way or the other some of one or the other layer right under the coating is gone.

On its first chassis dyno run this engine had lower oil pressure than I expected based on my other engines (and it has the GT3 pump, while one other has an ordinary 3.0/3.2 pump which makes good pressure), but not scary, don't keep testing, low. I made up pressure setting adjusters, which out of the box shimmed up the pressure setting spring some, and on the final visit to the dyno, they were higher. Arguably main bearings always get better oiling? But there was no differentiation between rod bearings (other than the one which got twisted), though the center main was cross drilled. This patterning isn't characteristic of low oil pressure, is it?

I was kind of hoping I'd find one of the pressure side oil pump seals askew, as that at least would explain oiling issues. But they were all normal. And all six piston oil squirters were firmly staked in place, so no help on that mystery.

Another possibility is that the coating made the bearings too tight? My measurements of the crank told me the journals were more on the low side, and that the coating wasn't going to raise it even to a minimum clearance, much less too tight.

The Clevit/Mahle site has a picture of "overlay fatigue," which looks a lot like what you see on my bearings. They list lugging (never happened here) and detonation (don't think so, as my twin plug spark settings are fairly conservative) as potential causes, along with the bearing simply not being strong enough for the loads. Their solution is for more robust bearings.

If I can use Clevite without having to regrind the crank and buy new rods, that sounds like a good plan.