454 Mag MPI Hop-Ups - Will this work ??
10-03-2007 | 03:55 PM
#12
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Joined: Sep 2007
Posts: 21
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The MPI on the small blocks and the 7.4 is not good to build on. The mag. engines have a decent system. Not as good as some of the aftermarkets but OK for 500-550 HP. They have 42 lb. injectors so you just need to do a mild remap on the ECU, add an adjustable fuel pressure regulator and tweak some.
I've seen people reprogram these systems - can anyone point me to the software/hardware that is needed?
The Holley systems are generic. They're also TBI based, which is fine and functions - but the direct injection systems run better in my opinion based on experience in the automotive world.
10-03-2007 | 04:30 PM
#13
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Joined: Jul 2005
Posts: 1,729
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From: Tulsa, OK
Just to note, we just re-did my 454 MAG MPI. We went with a 30 over pop up piston for about 9.6:1 compression, used Tyler Crockett's camshaft, springs, retainers and such. We went with RHS 320 Aluminum Heads with 2.25/1.88 valves. Then we had to up the fuel system with an Aeromotive pump and adjustable regulator. All this ran on the stock MAG MPI manifold with Crockett's tune. We made 501 hp @ 5200 rpm and 535 lb*ft of torque at about 4600 rpm. It pulls like a monster. We haven't gotten top end worked out yet as I have to prop test, and I think we have a fuel restriction from the tank to the new fuel system. Overall, I'm VERY happy with the setup. We sent the computer back to Tyler for some tweaking as well. Once that's done and the other bugs are worked out, we'll have 501 fuel injected reliable horsepower without putting a big strain on any of the engine internals.
10-03-2007 | 05:14 PM
#14
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Joined: Sep 2003
Posts: 1,225
Likes: 2
From: Fort Lauderdale, FL
just to give you my $.02, to give you an idea what you need to to to achieve 500hp + range. This engine was originally a 454 MPI EFI but no one was able to reprogram it for me so I converted it to support the new mods. Sounds like you are on the right track but MAKE SURE YOU remember to include upgrading oil lines and oil cooler.
GM 454
Dart Pro One Chevy Aluminum heads
Dart Single Plane Intake Manifold
CraneCams Roller Rocker
( I think this is the cam, I have to look it up to me 100% postive)
Crane Cams HYDRAULIC Powermax Camshaft Grind Number: HR-306-2S-14 IG
http://www.cranecams.com/?show=brows...tType=camshaft
JE 9.6:1 Compression Pistons
Stock Rods
Stock Crank
Blue printed and balanced
CMI headers
850CFM Carb
Mercury Marine 700SCI Oil cooler with all new -10 Oil lines
Dyno 550hp. I didn't build it, Gellner did and has all the specs and info on the original build. PM me if you have any more questions I would be gald to help you.
GM 454
Dart Pro One Chevy Aluminum heads
Dart Single Plane Intake Manifold
CraneCams Roller Rocker
( I think this is the cam, I have to look it up to me 100% postive)
Crane Cams HYDRAULIC Powermax Camshaft Grind Number: HR-306-2S-14 IG
http://www.cranecams.com/?show=brows...tType=camshaft
JE 9.6:1 Compression Pistons
Stock Rods
Stock Crank
Blue printed and balanced
CMI headers
850CFM Carb
Mercury Marine 700SCI Oil cooler with all new -10 Oil lines
Dyno 550hp. I didn't build it, Gellner did and has all the specs and info on the original build. PM me if you have any more questions I would be gald to help you.
Last edited by pkspx; 10-03-2007 at 05:19 PM.
10-03-2007 | 05:49 PM
#15
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Joined: Oct 2000
Posts: 1,382
Likes: 3
From: Spicewood, Texas USA
The difference is the intake manifold and throttle body. The non-mag 7.4 is a gm truck intake system designed to make great low end torque, but won't flow enough air to make much over 400 HP. The Mag uses a Merc intake and throttle body that flows much better.
What are the differences between the Mag and non-Mag EFI systems that make one good for a modified motor and one no good?
I've seen people reprogram these systems - can anyone point me to the software/hardware that is needed?
The Holley systems are generic. They're also TBI based, which is fine and functions - but the direct injection systems run better in my opinion based on experience in the automotive world.
I've seen people reprogram these systems - can anyone point me to the software/hardware that is needed?
The Holley systems are generic. They're also TBI based, which is fine and functions - but the direct injection systems run better in my opinion based on experience in the automotive world.
10-04-2007 | 08:23 AM
#16
Gold Member
Joined: Sep 2003
Posts: 1,225
Likes: 2
From: Fort Lauderdale, FL
Okay, I'm tired of hearing that I have to ditch my fuel injection for a carb to make any real power. How about this?
-Get rid of the MPI
-Replace heads with a good set of aftermarket heads, professionally prepped, ported, etc.
-Stock compression (maybe up to 9:1)
-Whatever cam would work good with this combo and still idle well (probably no more than 610 lift) with matching lifters, springs, etc.
-Holley Commander 950 multi-port fuel injection (I don't wan't to give up the easy starts and smooth idle)
Would this work and make some serious (but reliable) power? Are there many good marine mechanics that know how to make the Holley systems work?
(Okay, before anyone mentions it, I know all about the blower option and how it's the best bang for the buck, etc., etc.)
-Get rid of the MPI
-Replace heads with a good set of aftermarket heads, professionally prepped, ported, etc.
-Stock compression (maybe up to 9:1)
-Whatever cam would work good with this combo and still idle well (probably no more than 610 lift) with matching lifters, springs, etc.
-Holley Commander 950 multi-port fuel injection (I don't wan't to give up the easy starts and smooth idle)
Would this work and make some serious (but reliable) power? Are there many good marine mechanics that know how to make the Holley systems work?
(Okay, before anyone mentions it, I know all about the blower option and how it's the best bang for the buck, etc., etc.)
