ballon78

Looking to see if anyone has done a cam swap and reprogram ecm on a 350 mpi and if it worked out good. Stock exhaust, thru-hull. Thanks.

abmotorman

I did a 1999 350MPI. Cam and springs upgrade. I reprogrammed with MEFIburn. Gained 2 mph. Learned a lot. Don't expect much.

Young Performance

In order to take advantage of any internal work, you will need to change the exhaust. You won't see any gains from the exhaust alone, but it's necessary to realize the potential of other mods. The only way that you will see any appreciable gains will be by changing the cam, springs (and any other needed components like pushrods, lifters, etc.) and bump the compression. You can surface the heads while they are off changing the springs, etc. and raise the compression a bit. Obviously, you would need some tuning to go with the above. There is no one size fits all tune for those mods. You will need to get YOUR engine tuned. You should be able to find 50 or hp.

The other option is to install a supercharger like a Whipple or Procharger. I've done quite a few of both in the past and they make great power. You can easily get near 500 hp with either one.
Eddie

Trash

I went one step further, albeit on a 1995 motor. Stroker crank, heads (old heads were pre-Vortec), cam and my own tuning. Never dynoed new motor but netted nearly 12 mph on the big end. Stock style GLM exhaust, same used on old motor. Not sure what ECM you have but it is likely the 555 of which I can offer zero help. If you mod the motor the last place I would spend money on is the exhaust (for a small block).

Good luck.

airjunky

iTrader: (2)

Your going to need long runners if you want to go much beyond the ht383 factory roller grind n/a.which you are probably going to want to do ,if you are looking to make a worthy bump in power using the stock crank and 5.7 liters. Then there is the head mods. But the ole vortec is capable of impressive things ,considering its beginnings

BUP

iTrader: (9)

This is ECM 555 Motorola not a MEFI app so anything MEFI burn or MEFI will not work for your app.

IMO you are wasting your time. If possible buying a complete drop in 383 from Merc reman or up grade to a LS motor of something 400 plus hp if that would work in your budget..

Also you did not report if you have an Alpha outdrive or Bravo 1 or Bravo 3 ?

I would work on balance of your hull plus possible lighting it up ( take weight out) and prop testing for some extra speed. This will keep your very reliable 5.7L - 350 - reliable. Possible look at the bottom of your hull for hooks and any imperfections.

Trash

Lots of options here but you would need to either lay down a budget or a performance goal. Then we'd be able to give you more direction. In my opinion, your biggest deterrent to modification is the 555 controller. Limited 'hackability' .

phughes69

Has anybody hacked the 555 controller? I have a 2006 350 Mag with the 555 and would love to throw a pair of turbos at it but cant with the existing controller to my knowledge. Changing over to the MEFI is not worth it with the tune costing a couple hundred after that. Much easier to put a Megasquirt on it. But them I cant get the Smartcraft to communicate with Megasquirt.

Young Performance

Dustin Whipple at Whipple Superchargers and Mark Boos at Precision Marine. Both great guys.
Eddie

COOPS

iTrader: (2)

Ls motor and keep the 350 as a spare or until you work all the bugs out of the ls for a season. Then sell it.