from a previous thread skidmarkjunkies(a really sweet person) said that putting a 390 crank in a 331 would make a 412 caddy but he wasnt sure so I was wander if anyone knew if this was true and how hard it was and what it all would take and that would be a mean engine and the cars named junkyard kid so all the more put together the better.
That doesn't make any sense. A 331's got a 3 13/16 inch bore. If you bore it out to 4 inches, it turns into a 365, and if you then drop a 390 crankshaft in it, it becomes........a 390. The only advantage of going through all that on an early block is that standard shift setups are easier to find for a '49-'54 block than the '55-'62 style.
Heathen already hit the nail on the head but just to put a few more in the coffin lid, the 331s had 2.500" main journals, the 365s & 390s had 2.625"
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