So is it crank imperfections or something in the bearing MFG process? This was a K1 forged stroker kit and owner was set on using kings vs the supplied clevite.

The story here is a friend had a box fresh R block and had all the machine work done including align hone. He asked if he could bring it over and use my test stand to break in cam. It had crazy high OP from the start 90 idle and up from there so we knew something was wrong but it never got over 160 and cam broke in without issue.

After an oil change and maybe a total 1 hour run time with a few blips just over 4k it was the same high op. I told him imo it would not fly as it was and there was some material in the filter. Turns out there was a skirt issue that the mfg. went well above to correct.

When I pulled the crank I found two like this, was supposed to be king extra .001 mains but there were two STD halves in the lowers. This did not shock me because I myself have found this three times with King Bearings. They seem to understand it happens as they are quick to take care of it.

So I started to measure things further. He says he told the machine shop he needed at the end of the day .003 on the mains but in reality someone got crossed as there was a consistent .0015 TOTAL. (He used a shop not deep into performance builds and maybe that was part of the confusion, who knows)

So block went back to get align honed properly. Pistons got replaced by mfg. and King sent a new set of matched bearings and all was happy after that.

The pattern looks much like yours... Please keep in mind some of the dirt might be from these being in the "oops" box on my junk shelf for like 5 years, maybe longer so I had to wash and they have been tossed around a good but without care.