i have a blown 383 should i rebuild it and leave it a 383 or turn it into a 406, i want to run about 500 hp na,what do you guys think, and my rpms would be between 5200 t0 5600.

how are you gonna turn it into a 406? a 350 block won't take a .125 bore.

Could turn it into a 396

Guess that settles it then, I don't think the 500 hp is realistic either without some major aftermarket parts on a carb anyway, then theres a reliability factor.

i think he meant starting over with a 400 block. i don't think a GM 400 block is a good base for a high power marine engine. of course there are people here who feel that ANY GM block is insufficient for 1 to 1.5 hp per inch.

My 385ci setup is right under 500hp and has been completely reliable. To do this you need top of the line parts, Morel, Mahle, Lunati etc.. and built it to exact tolerances. You are not going to make NA 500hp and only spin 5200-5600rpms w/o the blower. I have to spin 6000-6300rpms. I would not use an original 400 block. By the time you buy the block, clean, magnaflux, sonic check, bore, hone etc..... you are well on your way to a DART SHP block that far outpaces an original 400 block.

You Can make a 396ci out of a 350 block with a 3.875" crank but it takes careful clearancing to not get into the water jackets when grinding. Not too many piston choices out there for that setup either. I almost went this route with mine but was alot easier doing the .40" over 3.75" crank setup.

for a 406 ,i would by a 400 block,and start from scratch,i already have the 383 it has 4 hours on it with 2 bad pistons,i would by new heads,intake ,ignition,carb,just seeing what other people have done,also it would be a hydralic roller cam.

If you're going to drag a SBC around anyway, why not make it as many cubic inches as you can. Go with the 406.

I have a 500hp/500ft lb 406.

Great mill with the right (expensive) parts and stone reliable.

A GM 400 block CAN be a great core, but it wont be easy to find or cheap. It will need to be splay capped to keep everything form moving around at the 500Hp level and the guys are right- unless you are sitting on a known cherry one right now just get an aftermarket block.


Uncle Dave

You can build a 406, with a 6" rod, 4.125 bore, +.134 raised cam with 50mm cam bores, lifter bushings, rotating assy, bearings for $3600.00 in parts plus balancing and assy.