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Black w/chunks missing could have been caused by a lack of lubrication that caused the bearing surface to overheat and begin to weld itself to the crank journal. The lack of assembly lube might have played a part in this, as could a lack of pre lubing the engine by spinning the oil pump w/a drill prior to first start up.
The "record disc" feeling is likely caused by grit or metal shavings and particulates left from machining or insufficient cleaning.
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