What if u take a 7.4L Mag MPI (385HP) and...

[Jamesbon]

What if u take a 7.4L Mag MPI (385HP) and stick on a pair of good breathing aluminum heads, bigger roller cam, 10:1 c.r. pistons and fresh water cooling? Will the stock fuel injection system compensate?

Doesn't the 502 Mag MPI F.I. system use the same intake/ecm/injectors?

Just thinking.....

[The Hedgehog]

What if u take a 7.4L Mag MPI (385HP) and stick on a pair of good breathing aluminum heads, bigger roller cam, 10:1 c.r. pistons and fresh water cooling? Will the stock fuel injection system compensate?
Doesn't the 502 Mag MPI F.I. system use the same intake/ecm/injectors?
Just thinking.....

It would like it! I think that they use basically the same injection setup. No, the system will not compensate. They primarily come with MEFI 1's and 3's and have to be reprogrammed. That is not a big deal. Eddie Young has around 2,000 programs for various setup's. There have been combo's set up with the 454 that get up to 500 hp. You will need to do the exhaust to handle the head and cams. Stock would revert pretty badly.

I don't know why more don't use this platform. Engines up to 1,000 hp have been built around it. I am having a 825+ hp screamer built right now.

[Jamesbon]

It makes sense to me too.

Were you running with us in Sarasota?

[The Hedgehog]

It makes sense to me too.
Were you running with us in Sarasota?

Was not me. It has been quite some time since I have run down there. Maybe next year once I get a couple of projects complete I can get down there. I plan to start getting out and about more.

[The Hedgehog]

The intake runners are the only downside if you want to stay N.A. They were designed by Lingfelter to generate good low end torque. They do. The long runners don't like more than 5,400 RPM (Neither do the 500 EFI runners). You can have them cut down if you want. If you go boost the sky is the limit.


These motors like boost. Nice forged internals. I ran a Procharged 502 for a couple of years. It has just been torn apart. The only thing I would have done differently for that setup is run a thermostatically cooled oil cooler.

[VetteLT193]

The intake runners are the only downside if you want to stay N.A. They were designed by Lingfelter to generate good low end torque. They do. The long runners don't like more than 5,400 RPM (Neither do the 500 EFI runners). You can have them cut down if you want. If you go boost the sky is the limit.
These motors like boost. Nice forged internals. I ran a Procharged 502 for a couple of years. It has just been torn apart. The only thing I would have done differently for that setup is run a thermostatically cooled oil cooler.


I think the Procharger is the best value. Plus, if you decide to sell the boat you can remove it and sell the procharger separate and still get back at least half of what you put into it. If you do all the other work to the engine, you'll be out just as much (if not more) money and you'll be lucky to get back 25%.

The engine computer are like early car systems, not a 'learning' unit, so as Big Green already said, it's going to have to be programmed.

[BUIZILLA]

IMO, I wouldn't touch the shortblock or pistons..., mild cam, heads, exhaust and reflash, and go play... great bottom end to build from

[VetteLT193]

IMO, I wouldn't touch the shortblock or pistons..., mild cam, heads, exhaust and reflash, and go play... great bottom end to build from

The killer is by the time you are done with exhaust and heads alone you have surpassed the price of a procharger.

[The Hedgehog]

The killer is by the time you are done with exhaust and heads alone you have surpassed the price of a procharger.

Yep, Procharger is the way to go. I have talked to many that have done heads and exhaust for 5 mph. The Procharger gets you at least 10.

One thing to consider is that you will want to do the head gasket regardless. Makes you think about other mods once you pull the heads. Like Buzilla says, the short block is good to go.

With the 502, you can do a blower, heads, exhaust and cam for a 700hp screamer with no need to go into the bottom end (as long is it is relatively fresh). That say a good bit.

[gcarter]

So how much better are a set of high end $$$ aluminum heads than the stock HI PERF iron heads.
I have the results of a flow bench test on my heads off the Testa Rosa.
Is there a point of comparison?????

[VetteLT193]

So how much better are a set of high end $$$ aluminum heads than the stock HI PERF iron heads.
I have the results of a flow bench test on my heads off the Testa Rosa.
Is there a point of comparison?????

Hi performance heads will look great when doing a 'paper comparison', but you really need the whole package to take advantage of it. To start off with, a good cam.

When you're supercharging, parts like performance heads make an even bigger difference, but it's all gotta come down to what you are trying to achieve. It's always cheaper to figure out the end result first and build the engine accordingly.

[The Hedgehog]

So how much better are a set of high end $$$ aluminum heads than the stock HI PERF iron heads.
I have the results of a flow bench test on my heads off the Testa Rosa.
Is there a point of comparison?????

I have been told that with some work iron heads can flow well. I was considering using them in my winter project. It is more than just flow that comes into the equation. I was told that if I wanted to make north of 750-800hp they would get hot spots and detonation would be an issue. Additionally, you can use a higher compression ratio on NA engines for that same reason. Oh well, at least the extra $1,600 will make the boat lighter too.

[gcarter]

I was just wondering, but I am planning on staying N. A.

[The Hedgehog]

I was just wondering, but I am planning on staying N. A.

Whatever you get from bumping the compression 1 point or something like that. Nothing huge. What 30-40 hp. I am sure that someone around here knows that number.

It is like Mr. Vette said, the real payoff comes when you start upping the ante.

[gcarter]

C/R= 9.8:1,
Cam is at upper limit of what's reasonable w/Q&Q,
Gill/Mercruiser exhaust manifolds
Will eventually move into a Holley 850
But that's about as far as I want to go.

[Jamesbon]

Great info. fellas.

dollar for dollar the procharger is the way to go, I guess.

We'll see what happens if the sun, moon and stars continue to align...

Dropped her off today to have Latham dual ram external hydraulic steering installed. Will post pics once she's home. Had to have a couple stainless parts "fabbed." More on that later..

Must say, I have enjoyed the trouble free, fuel sippin qualities of the bone stock set up that's in her now. (3 mpg overall avg.) Even with a wild blower motor or higher compression BBC, I doubt the fuel consumption would diminish much...??? Might even improve a bit... But I can't stop the yearn to have a RADICAL, LOUD high c.r. or blower motor making music in the hatch.

The only time I've run the piss out of her consistently was the last get together in Sarasota. You guys know one speed, WFO! :) With the sometimes nasty water down here we usually run 20-30 mph with intermittent blasts as I'm trying to smoke someone else. LOL!

Once the Latham steering's installed, I hope to focus on the poor 'ol GT. Deck's on and waiting to get stretched a half inch and fastened down.

I've looked at the GM 502 short block for about 4K. That also seems like a formidable base for some alum. heads, wild cam, carb. and FWC on pump gas.

[The Hedgehog]

It all depends on how fast you want to go.

I would set a mph goal and figure it out from there. If you think that you may want to up the ante take that into account. You can build a good base with big heads, a good cam and exhaust. No problem to get 500hp that way. It will have that nasty mean sound. If you maximize it by taking an extra point or so in compression then you are done. Leave the compression down and you can tap in an extra 200 ponies if you want to go wild.