Im still researching my next engine build and was pretty well set on a 509 Dart block base. (4.5 bore x 4.00 stroke.)

I was wondering if anyone has built a large bore, short stroke BBC? I was thinking of using the 427 crank (3.76 stroke) with a 4.5 bore for 478 ci. Has anyone built this combo or know anyone who has? Thanks.

With boats torque is the key. I would not do the 427 crank. Dont make any sense. If you are starting new I would do a 540. Will not cost any more money and will make great power with good reliability,
4.50 Bore
4.25 Stroke
.250 long rods

My 2 cents

Ditto!

540's are my favorite naturally aspirated motors. Big Torque, and still love to rev. My last 540 buildup made 665/tq at 4600 and 665/hp at 5800. This was a really docile motor around the docks, and would scream on the top end.



Chris

P.S. The motor was speced out by Bob Madera aka RMbuilder and I would recommend him highly.

Thanks guys, on the 540 build, are these typically done on a 9.8 block? It seems most aftermarket builders go to the tall deck for 540 and above.

The typical 540 buildup is done with a 9.8 block... ie a 502 block with a 1/4 inch longer stroker crank. The buildup costs about the same as building a 502, but the difference in torque is substantial. There is generally little or no extra machining needed on the block to clear the crank, and stroker kits for this motor are readily available. I bought a new 502 block from my local chevy dealership, when they were on sale from GM for about 1700.00. They seem to go on sale about once a year.

Chris