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get ur cam checked for straightness. a friend of mine had an engine built & there was babbit material on the edge of all his cam bearings. his cam was 1/4 thou out of being straight. something u should check. u must be getting oil to the top end cos u didn't mention about any burnt shafts.



not sure why .00025 TIR would bother anything.
the OP did say;
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The engine fired right up and ran for 25 minutes at 2,000 – 2,5000 RPM to break in the cam before the valvetrain stared seizing.



machine shop owner and engine builder