Fueling Up To 700 Horsepower On A Budget Fox Body With Aeromotive


Aeromotive sent us everything we need to build a 700 hp capable fuel system.

As we get Project Rehab, our 1991 Fox body hatchback, closer to rolling under its own power and making its way to the track, there’s a few areas left that we need to address. One of those is the fuel system. While we’re planning to eventually go respectably fast in our lightweight, budget Mustang, we’re not in need of a monster fuel system to do it. For a solution that won’t break the bank, but will provide all the fuel we plan on needing, we turned to Aeromotive for help.

Aeromotive offers a variety of fuel pumps and complete fuel system options for Mustangs and other musclecars. However, we’ve already installed a brand new fuel tank, and while it would be cool to put in a full Stealth system or even plumb up an A1000 hooked to the stock tank, or a fuel cell, we were looking for something that wouldn’t be overkill for our car.

Sizing And Upgrading

The factory fuel system will only support around 500-550 hp, even with something like a 255 lph pump. Once a car has reached that point, it’s time to look into an upgraded fuel system. -Jared Cox, Aeromotive

Determining the right size and capacity for a fuel system is not just a matter of selecting the largest pump and going on full overkill. Conversely, relying on too small a system is asking for trouble as your project progresses and makes more power.

Aeromotive’s Jared Cox says that even with a pump upgrade, the stock Fox body fuel lines will only support so much power. “The factory fuel system will only support around 500-550 hp, even with something like a 255 lph pump. Once a car has reached that point, it’s time to look into an upgraded fuel system.”

Cox says most enthusiasts make one of two mistakes, which turn out to be complete opposites of each other. The first is assuming the stock fuel lines and a drop in replacement pump will be adequate to power high output engines. The second is going overkill on a fuel system. While having more fuel than is necessary is a good safeguard, having a system that is constantly dumping a large volume of fuel back to the tank via the return line is overkill, and can lead to other issues like the fuel boiling in the tank which can lead to a pressure drop, cavitation, and fuel starvation.

Plumbing Our Fox

Aeromotive sent us their Stealth 340 in-tank fuel pump as the foundation of our fuel system. This pump, Aeromotive part number 11140, can be found at Jegs.com as part number 027-11140. The pump can be used with the stock Fox fuel system hanger. In our case, we paired it with one of Spectra’s fuel pump pickups that uses a 3/8-inch supply line. This will allow us to use an adapter to run -6 AN fuel supply line. According to Cox, this pump is capable of flowing more than 340 lph at 40 psi. It’s turbine motor is highly efficient, and it is compatible with either EFI or carbureted engines. You can even use this pump with a pulse width modulation type controller, although that’s probably overkill on a system such as this.

Top Row: Left and Center: We used a Koul Tool to build our lines, holding each fitting in place. Right: This quick connect fitting and the fuel rail adapter are two essential fittings to our system, allowing us to use the stock tank, and the stock fuel rails. Bottom Row: Left: The Stealth 340 pump installed in the Spectra hanger and ready to go in the tank. Center: The finished installation in the tank. Right: The quick connect fitting not only makes this system possible, but will also speed up maintenance, repairs, or upgrades in the future.

We mounted our fuel filter inside the passenger side strut tower. This will allow easy maintenance, fuel line routing, and keeps the filter and lines away from heat sources and moving parts.

Cox helped us set up a medium sized system, that would fit our budget project build, and meet the demands of our car. “You can think of this like a little brother to the bigger Stealth systems. It will support up to 700 hp with EFI and forced induction, and the pump is capable of supporting up to 850 hp with forced induction on a carburetor equipped engine, with the proper size lines.”

While our pump has a strainer/sock included with it, that’s no replacement for an inline filter. In that department Aeromotive supplied us with Aeromotive part number 12301, Jeg’s part number 027-12301. This filter is more than capable of handling the demands of our fuel system. The 10 micron element means that the filter won’t cause a restriction in the line, and the mounting bracket, part number 12701, allows us to mount the filter almost anywhere.

Left: The intake plenum must be removed to gain access to the fuel pressure regulator bolts. Center Left: The OEM regulator was long gone, replaced by this parts store unit, just because it's red, doesn't make it an Aeromotive part. Center Right: With the Aeromotive regulator installed, it's easy to see the difference in the two parts. Right: Final installation of the regulator and gasket.

Power Under Pressure

“As pressure in the fuel system goes up, current draw increases. The Stealth 340 draws about twice the current of the stock pump, so it needs a proper circuit to power it” says Cox. This means the factory fuel pump relay and circuit aren’t going to be up to the task of powering our system. Aeromotive’s fuel pump wiring kit, part number 16307, is our solution. This heavy duty kit supplies a new relay and heavier gauge wiring to supply all the juice necessary to the pump. Wiring it is a matter of connecting the two positive and negative terminals to the pump connector, and the remaining ground, trigger, and power supply wires appropriately.

To control the pressure in our system, Aeromotive sent us one of its fuel pressure regulators, compatible with Ford EFI systems. Part number 13103, is adjustable and includes an NPT port for mounting a gauge either directly to it, or remotely. This regulator is a direct replacement for the factory part, requiring no adapters or additional work to make it fit. Since this regulator is adjustable, whereas the stock unit is not, it will allow owners to set the fuel pressure based on their application.

We’ll be using the stock metal return line to send fuel back to our tank. Aeromotive supplied us with all the hardware necessary to use its -6 AN fuel line for the supply side. Why can we use the stock return line but not the stock supply line? The -6 supply line is necessary to support the fuel volume we need to feed our engine as we increase the horsepower. However, Cox pointed out, “As fuel pressure goes up, flow goes down, so in this application the stock return line is all that’s necessary. In a carbureted application, because you’re dealing with significantly less pressure, and typically more volume, we recommend using similar sized feed and return lines.”

We wired the fuel pump relay power wire through our master cut-off switch. This is per NHRA requirements, as well as a good idea for safety since it allows the pump to be shut down with the rest of the car from the switch.

Top Row: We mounted the fuel pump relay and circuit breaker in the trunk, near the cut off switch. This makes for easy access when servicing. Bottom Row: Left: We disassembled a stock replacement fuel pump connector and used it to make a simple and reliable connection at our fuel pump pickup on the gas tank. Right: The final connection needed to complete our installation was to install and connect our fuel supply line using the supplied fittings from Aeromotive. This is combination of both the spring-lock fitting to the fuel rail, and a 45 degree angle fitting to route the line away from the distributor.

Parts List

11140 Stealth 340 Fuel pump

12701 Fuel Filter Bracket

13103 Fuel Pressure Regulator

15118 Fitting 3/8 Quick Connect to -8AN

15124 1/2 inch fuel rail to -6AN

15605 -8 to -6 reducer

15609 -10 to -6 reducer

15650 -6 straight fitting

15651 -6 45º fitting

15703 Stainless braided hose

16307 Wiring Kit

12301 10 micron filter

We were also sent a quick connect fitting, part number 15118, for the fuel pump pickup that will allow us to easily disconnect the supply line any time the tank is removed. Cox also included the necessary fitting to connect the new fuel supply line to our factory fuel rails, part number 15124. Since our engine is currently stock, we won’t need to run aftermarket rails right now. As our project progresses if we choose, we can upgrade the fuel rails later.

We spent an afternoon installing this system in Project Rehab. The most difficult part may have been figuring out exactly how we wanted to route our -6 fuel supply line. From there, the rest is a pretty straightforward installation, which we’ve outlined in our photos.

With our fuel system completely plumbed from front to back, all that’s left to do is tie up a few loose ends to get the engine started. We’ll set the fuel pressure using our new regulator, and be ready for our next round of upgrades on Project Rehab.

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About the author

Don Creason

Don Creason is an automotive journalist with passions that lie from everything classic, all the way to modern muscle. Experienced tech writer, and all around car aficionado, Don's love for both cars and writing makes him the perfect addition to the Power Automedia team of experts.
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