Since the main bearing bores on a stovebolt engine are four different diameters, line boring can be a real challenge. I have home-brewed a few machining fixtures to allow me to narrow the thrust faces of the #3 main bearing web on a 216 engine so I can install a 235 crankshaft. That same setup could be used to guide a small rigid cylinder hone in the rear main bearing bore to adjust the diameter, while maintaining sufficient alignment with the other bearing bores. It would be a tricky, but doable procedure, I believe.

I have a portable line bore setup that could be used to do a conventional boring procedure, but that would require doing four separate cutter diameter settings. The fit of the timing gears between the crankshaft and the cam is also a critical measurement because the centerline of the crankshaft is moved slightly in the process. Most of the material must be removed from the bearing caps, while little or no material is removed from the block.

I'm planning to add this small diameter rigid hone setup to my line bore fixture to use on stovebolt blocks:

www.ebay.com/itm/225914437965

Jerry

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