It all depends on how well the block (and the different cap) were machined in the first place. On the blocks that I'm going to convert to small block 400 main bearings with reducer bushings in the block and the caps, I'm pretty sure I'll need to rough out the new dimensions with a line bore, and then line hone the finish diameter. I just spent $3K on a line hone mandrel about 4 feet long to do the finish sizing. The end result will be all four main bearings the same diameter, and readily available bearings that cost around $50.00 a set. I'll also be able to salvage "worn out" crankshafts that have been ground way undersize without welding on journals.
Jerry
