I have a 318 5.2 in my 1972 duster im looking for a build that will give me 400+ hp

 

Are you hell bent on keeping the 318? It'll be much easier starting with more displacement.

 

There are blowers, turbos and nos! Try a big block, You will like it!

 

Its the orgininal engine thats why i want to keep it

 

Here's an informative thread on the 318...................

http://www.forabodiesonly.com/mopar/...d.php?t=194446

 

Ok, you have the original 318, so you want to keep the originality but you want to modify the car (and all that goes with it) for forced induction...?

Bsides that, you will need to build that engine first before you put boost to it. Your 72 318 is low compression, cast pistons and rods, cast crank, small port and small valve heads. You can use a 340 forged crank (same 3.31" stroke and bearing sizes) but you'll need pistons and rods to match (318 has a smaller bore). Then you'll need 340/360/W2/aftermarket heads to take advantage of the build/boost. You'd be better off starting with a bigger better built engine. Hell, you'd probably better off building a magnum based 408 stroker, better heads, better cam/compression, more displacement.