what is the largest crank you can fit in a 350 block? And whats the max displacement yuou can get out of this crank.

 

The August '02 edition of Hot Rod magazine had an article called "25 New Ways to Build a Small-Block Chevy". Well, not much of it was really "new", but on page 38, there's a box on possible dimensions. For stroke, they say, "We've seen strokes as ... much as 4.250 (...requires a raised-cam block)."

For all practical purposes, with a production 350 block the largest stroke you should consider is 3.75" because of rail and cam clearance issues with the rods. If you get some expensive pieces, you can get away with something longer, perhaps.

On page 44 of the same edition, they say, "Here's one we're actually working on: the 454ci small-block. The combo depends on a 4.185-inch bore and 4.125-inch stroke, which means an aftermarket block and a raised cam are needed to accomodate both. Additionally, this setup works best in a tall-deck block so longer connecting rods can be used..." Obviously, you're looking at some big bucks there.