small block HELP...keep spinning the same bearing

[Jac Mac]

John, As Keith has mentioned sometimes things happen, for the most minor of reasons, that this has on the same bearing/rod on more than one occasion is a concern & I am sure neither you or the builder want a repeat performance.

Rather than rushing to get it back together, allow him some time to 'look' for what might be the cause.

A couple of ideas you might like to incorporate prior to & during assy.

1. Fit the crank/cam/lifters/oilpump/ and fit the pan without gasket. Now fill the pan with 20 or 30 weight oil, fit filter & prime oil pressure while turning crank slowly-observe thru the cyls that oil is flowing from All eight rod journal feeds and in similar amounts.
This serves three purposes-that you have no blockages & as a final flush of the oil galleries in the motor, & that you have not left any internal gallery plugs out.

2.Once the pistons/rods are fitted & torqued, ensure that each rod has side clearance on each journal and that both rods can be moved freely by hand to check this on any journal, while doing this check that the small end of the rod has side clearance between itself & pin boss of piston. By doing these checks you eliminate any bind or preload that could cause scuffing & failure of the bearings.

3.Like Keith I always start & test run on a test stand with radiator or cooling tower. It eliminates that 'quick run around the block' factor and makes retorque & valve spring replacement after cam break-in a lot easier.

cheers & good luck.