383 MPI builds
 

Hey guys, I've decided to go a new direction with my small block builds. They are 2002 350 mag MPI's with IMCO powerflow exhaust as they sit atm. My original plan was just pistons, rods, cams, heads and ecm tunes... After alot of thought, I think I'm gonna go for it and make them 383's.
Rough build list would include
-Forged rotating assembly with 6 inch H beam rods, Dished pistons
-High volume high pressure oil pumps with bigger pans and oil coolers
-crower Hydraulic Roller 221/230 cams on a 114 LSA (TBD)
-AFR 190cc vortec pattern heads 65cc chambers (purchased)
-scorpion 1.5 roller rockers with 7/16 screw in studs
-IMCO powerflow exhaust with 12 inch Tails
-stock MPI intake, throttle body
-custom tall flame arrestor
-tuned ECMs through whipple or whoever else can tune the 555 ecm.
My goal is 400-425 HP
Trying to work in a budget of $10k
any thoughts or insight on the builds or recomended parts would be greatly appreciated!
Here's a pic of the Heads I bought
https://cimg8.ibsrv.net/gimg/www.off...dfd509724c.jpg

How much cfm does your intake/throttle body support? Otherwise everything looks good to me.

Not sure but as far as I know the 383 mag stroker that Merc sells is the same intake and throttle body as the 350 and 6.2

If you haven't searched or seen this thread.
It's pretty much what you're doing. Except he used stock heads and aftermarket intake.
https://www.offshoreonly.com/forums/...d-project.html

[QUOTE=Franks292;4843645]Hey guys, I've decided to go a new direction with my small block builds. They are 2002 350 mag MPI's with IMCO powerflow exhaust as they sit atm. My original plan was just pistons, rods, cams, heads and ecm tunes... After alot of thought, I think I'm gonna go for it and make them 383's.


Find our your injector size and ensure you have enough headroom to support the power you intend to obtain.

DO NOT change props yet. Get the motors running and dialed in on the stock/original props. THEN see if a prop change is required. You may find that you can simply spin the original props at a higher rpm and without this baseline you will be chasing your tail on props.

[QUOTE=Trash;4843708]I actually love the stock props I have. I just had them cleaned up, balanced and polisned by a local prop shop. I was thinking the same thing, get comfortable on the stock props and see how she runs. This is how the stock props are, perfectly trimmed in 1ft chop
https://cimg1.ibsrv.net/gimg/www.off...bb18f65c0f.jpg

I think you are going to be knocking on the door of 440 horse once sorted. I got 407 horse on a 383 with the smallest runner Dart Iron Eagles. Like 165cc. I did port them though. Do all the little things and it pays off. Port match your intake, knock off the casting flash and any shrouding in your heads and maybe smooth out the valve guides inside the bowls. Don't open the runners though, that's your intake velocity. Get a perfect quench height between .035 and.045". Work out your engines to bring about 8.6:1 dynamic compression.
One guy on here did a big inch small block with a carburetor and more cam than that. Did it with Johnson variable duration lifters that don't raise fully at idle, which in turn makes the cam act smaller and allow a bigger duration without reversion. You probably would have your ecm doing backflips trying to operate that though.
My cam is 218/224 at .050 with 113 lobe separation. Stole the idea from SB on here. He had it in a 355 I believe.
There is plenty of oil pressure and flow in a normal pump, or even a high vol. I'm getting 60 to 80 psi cold with a high volume pump that has a 58 pound spring. And 40 psi hot, but I do have a thermostatic oil cooler.

​​​​​Congrats on the 383 decision.

With AFR 190 Vortecs, you're going to have north of 425, with a lot of bottom end.
221 @50 int will keep the tq curve lower.
Make sure you get enough lift. Consider 1.6 rockers. You want to let the AFRs breathe.

With the smaller cam, you can use the right side of the peak HP curve for peak RPM, and still have an efficient cruise.

If I could make 450hp I would be ecstatic, but I'd be more than content with 425. I am considering an aftermarket intake and throttle body to take full advantage of the new heads and bigger cubic inch.