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Hello everyone! New to the forum. Used search function but haven't found much relating to what ive got goin on.
Little back story. Engine was a free hand me down from a drifter friend. spun a rod bearing (im assuming oil starvation) he replaced the parts that failed (rod and bearing). Turned the engine back on and the oil pressure went lower and lower as the engine warmed up to the point he shut it off and cut his losses.
Fast forward to now im digging in to it and found the 2nd main cap to have some blueing on the center of the cap about an inch in diameter. Guess my question is can the blued be reused if verfied good with an align hone? Or would i have to get another one? I know some machine shops dont usually like using mains that werent original from that block🤷♂️. Any help appreciated! Thank you!
First question is, what are you doing with the engine? If it's a basically stock rebuild and the machine shop says it's machineable to spec, run it. If you plan on boosting it or whatever, go find another engine. LM7s are a dime a dozen, it's not worth the potential headache. I'd guess it's probably junk if it spun a main bearing bad enough to blue the cap, though.
If the crank walked far enough to rub the cap, the thrust is long gone and you’ll also have rods rubbing together at the big end…check those rod cheeks for blueing also.
Well boys, glad it was a free motor hahaha. Check out these apples. The bearings were new king bearings. Im wondering if he didnt set the thrust or check for endplay. The cheeks of rods look great. No rubbing or marring or discoloration.
Lol rod failure debris definitely a contributing factor hahaha! Honestly though im wondering myself what would cause it to make that much contact with the main caps. Didnt have much time to investigate. Ill follow up with my findings. Seems this has turned into a science project / crime scene rather than an engine refresh lol. Im thinking none of the bearings were seated/clearanced properly or wrong size🤷♂️.
Is it front of the trust bearing material the one that got chewed up? If so, that much movement of the crank backwards will also wipe out your transmission's pump if it was an automatic.
Not sure if it's a manual, don't have any experience with manual transmissions myself.
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Blued 2nd Main Cap on LM7 
. This was is the 2nd main cap bearing.