454 Mag MPI Rebuild - HP estimates?
 

Did a full rebuild on my motor but didn't get to put it on the dyno, looking for guesses on the new HP. There are a lot of discussions on mods with the carburated version but not as many with the MPI.

454 Mag MPI (originally 385 HP, w/flat tappet cam)
10:1 Compression
Bore .030 over
EMI Exhaust
Inconel Valves
H-Beam connecting rods
Mahle pistons
Liberty Rocker Arms
Manley Push rods
Edelbrock lifters
Hydr. Roller Cam
Intake Net Lift .569"
Exhaust Net Lift .561"
Intake Gross Lift .335"
Exxhaust Gross Lift .330"
Duration @ .050"


Also, how do I read the balancing results for the Bobweight card and final spin numbers?

Thinking 430-450. No expert here but I do think you will need an adjustable fuel pressure regulator or you may run the risk of running lean.. You might ask Rylar about the exact pressure but prob 45.

Chris

you need a ecm reflash before or on the dyno or you will run lean and burn a piston!

Absolutely in agreement...Do you know the ecm type..AKA mefi 3..4..Or a 555 system..Or is it aftermarket

Ecm
 

Still running the stock ECM. The motor had 670 hours and needed a rebuild, I wanted to do as much as possible without modifying the ECM or risk putting too much power to the drive (Bravo 1).

Have I done too much w/o changing out the ECM and how will I know if it's running lean?

I have the exact same motor you do and had mine rebuilt last year. The shop put a different cam in and the ecm kept putting the motor in safety mode. You bumped your compression and changed the cam specs. You will NEED an ECM reflash or it won't run right.

You definately need to have the ECM recalibrated. You will also need to run 93 octane fuel with 10:1 CR.

You will know its lean by the holes in the pistons.

With the amount of money I spent on the reuild I don't need holes in the pistons. Motor is being put back together today on the floor, I'll see how it reacts without any stress put to it.

Thanks for the feedback. How much was the reflash and how much HP did you end up with?

Winter is slowly creeping up, I'm hoping to test this thing out soon. By the way, it's in a 27 fountain.

Hp
 

Good news is thats a boat that reacts well to horsepower..Some boats adding 100 hp might get you 6 mph but I think you will get a solid 10 maybe more.


Chris