4.100 might be pushing it on the bore with that stroke. I was thinking 4.040 bore for strength and .060 over would be max. i'd like to get some input on this topic from someone who has tried these different crank combos on a dyno or at the track to get some more real world info. don't want to spend a bunch of money on extra machine work to only find out it runs no better than my currnet 408. Andy, you out there? any other engine builders that can add to this?