No flack here, sixpak,
However, since these old 6s have a longer crank, and only 4 main bearings, it is more susceptable to twist and vibration. Having a crank balanced is good insurance, to make sure the crank isn't WAY off balance to start with. Plus balancing is done with the rings, rod bearings, damper and flywheel in mind, so it corrects for those tolerances as well.
Trust me, bad crank bearings pull major vacuum.
My rebuild is 7 months and counting. Bad main bearing killed my 235.
chip
