Originally Posted by superchevy1080
Put a good stroker crank in that 400, I believe you can get a 4.125 crank for around 300 bucks but don't expect a cheap crank to handle high rpms only push cheapies to 6000 to 6500 rpms. You will also need 6.00'' rods I don't remember what piston pin height you will require but the rule of thumb is longer rods are stronger than shorter rods. As for heads you can expect to gain around 15 to 20 hp from slapping on a set of vortec heads; that's a conservative number because intake cam and pistons have a big effect on how efficient a set of heads are. A good street-able cam is .450 to .500 lift and for compression I prefer around 10.5.1 but recommend only running premium fuel. When you put a larger cam in an engine it allows for more flow of air and fuel and because of the increase in volume the piston now has to compress more fuel and air to create a larger explosion so an increase of compression ratio will make a more violent explosion which translates into more HP. Just my .02
A 4.125 crank should make her a 441ci sb
To further my reply though, I would not attempt to put even a 4.00" stroke crank in a stock block 400, let alone anything larger. 3.875 yes, but that would be the largest I'd want to go on a stock block.