Installing EFI on perf 331

[latrucker]

I have a carbureted 331 making 365hp at 6000 rpm and 385 ft/tq at 3800 rpm (measured at the flywheel). This is with a 680 cfm carb and a weiand street warrior intake. Converting to 89-93 mustang EFI with explorer gt40 intake. What things do I need to consider changing in the stock equation to support the HP and TQ of my motor. It's not tremendous power but leaps and bounds ahead of stock. I am assuming things like injectors and throttle body will need to be changed.
I will never see 6000 rpm pulls but want to stay on the safe side and be prepared in case it does happen. I know I will need a tune when all is said and done. Hoping someone can educate me a little. Really fed up with carb but want to know what I'm getting into with performance EFI. Spent lots of $ to build a nice stroker and don't want to limit its power potential and don't want to bite off more than I can chew either.

 

[Broncobowsher]

There are a lot of opinions on this. The GT40 intake chokes out about 350 HP if I recall correctly, so you will be using the full potential of the intake.

Injector size, 30Lb should be safe up to about 400 HP on gasoline. 42s are a commonly available injector as well. So I would recommend 30-42 Lb injectors.

Now a MAF capable of flowing enough air and properly metering it. Basically you need a MAF from an application with about the same HP. Off the shelf Lightning MAF fits the bill. All off the shelf parts that can be serviced in the future if needed.

Others will have slightly different recipes and favorite parts to mix together.

 

[EFI Guy]

Broncobowsher nailed it. I'd run the GT40 intake. No lightng MAF, I'd get an OEM 05+ Ford slot MAF and drop it in a 3.5 inch tube. Use OEM Ford injectors not Feebay Chinese knock offs.

For tuning grab a Quarterhorse, ask me for a base tune. Then drive it on up to Baton Rouge for the Moates tuning class and you may get to fine tune it on the dyno.

 

[xcntrk]

Here's a great read on properly sizing EFI components based on estimated HP output:
http://www.fordracingparts.com/download/tipsPDF/ProperlySelectingEFIComp.pdf

 

[latrucker]

Thanks to all 3 of you, great help and exactly what I needed to know. Once I upgrade to the 30lb injectors and MAF sensor, will I also need to upgrade the throttle body and modify the intake to accept the bigger stuff or will the stock TB and manifold sizing work? Also wondering once I get it all sized, running and tuned will it be a good dependable setup or will it be like my carb setup where I always have to tune and tinker on it. Really want to use my 331 but want a good dependable setup that has power and can use is as a daily driver if I choose to.

 

[Broncobowsher]

You should collect all the parts before you start the EFI swap. Get it tuned as a final package.

You never specified your planned throttle body size, but sized correctly for the rest of the parts. The larger it is the more potential for HP but the harder it is to control just off idle. 65mm would be the smallest I would even try, that was stock Explorer size. I forget the bore on the intake, but any larger is pointless.

 

[latrucker]

Broncobowsher nailed it. I'd run the GT40 intake. No lightng MAF, I'd get an OEM 05+ Ford slot MAF and drop it in a 3.5 inch tube. Use OEM Ford injectors not Feebay Chinese knock offs.

For tuning grab a Quarterhorse, ask me for a base tune. Then drive it on up to Baton Rouge for the Moates tuning class and you may get to fine tune it on the dyno.

Thanks for the Info EFIguy. What does it take to adapt the slot MAF to the mustang efi? Does it plug right in or some modification required? What is the charge for a base tune to the computer because I will need to get it done? Also, going pick all the efi stuff tomorrow from a local guy that has everything. What computers are best to use. I know everyone wants a9l but it is not a must to have that particular one. What are the other codes that would work just as well? Thanks for any help

 

[EFI Guy]

Computer code doesn't matter if you are tuning it, just needs to be a 93 or earlier mass air PCM.

The slot MAF uses a different plug and different housing. The plug can be sourced from the boneyard and soldered in or adapters can be purchased new online. Type "slot MAF" in to Google or Feebay and you will see a ton of different housing options. The flange for the sensor can be purchased separately and mounted to your own tube as well.

Pm me about the tune.

 

[FlogginHarvey]

Hey there,

Just popped a pm on some details on your 331 build...trying to work through one here...