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by Phil Ross (aka. HoosierBuddy)

In Part I of this article series I discussed the values of ditching the factory mechanical fuel-pump for a more modern electric fuel pump. Not only was I condoning the benefits due to the simple advantages of modern design, but I was responding to personal experience with the failures of an old mechanical fuel pump that simply was not cut out for the demands of a pumped up small block Ford. My intentions were not only to meet the demands of the current engine, but to look ahead and ensure the new fuel system could supply my anticipated 347 EFI motor. As a result I spared no detail and set out to nstall a late-model Mustang "in tank" style EFI fuel pump. This took significant modification of the early Mustang fuel tank, which I covered step-by-step.

Part I ended with tank converted and fuel-pump assembly installed and ready to go. In this article, the second of the two-part series on fuel-system modification, I finish the items require to drop the tank back into my 1965 Mustang and also tackle the fuel lines. Since high-pressure EFI fuel pumps require recirculation of the fuel, upgrading the fuel lines from the tank to the motor, and back, are absolutely neccesary. I will show you how to design the system and install the lines.

System Design
This diagram shows all of the major parts of our return style fuel system. Note that our pump now supplies pressurized gasoline to a return-style fuel pressure regulator. The pump will constantly circulate cool fuel through the system. While the diagram shows a carburetor, this system will also work with EFI. However, a carburetor needs around 5 PSI and modern EFI systems need about 40 PSI. The regulator must be designed to provide the required fuel pressure.

In the first part of this article, we mentioned that our new, larger, twenty-gallon fuel tank would require a new fuel sender. The fuel sender assembly also includes the fuel pickup for the stock fuel line. Our Tanks Inc system does not need this pickup so it must be plugged.
Here, the tank filter is cut off the sending unit with a tubing cutter.

The tank side of the fuel sender stub is pinched shut and then welded closed. We also installed a plug on the other end of this tube, just to be doubly safe.
Before the tank could be mounted into the trunk opening, the old sealing material was removed. After a little touch up paint on the mounting lip, a bead of silicon adhesive was used to seal the tank to the trunk floor.

The tank is fastened in to place with sheet metal screws.
Here's our first bit of aluminum tubing. Two 25' rolls of 3/8" fuel line were required for the project. This first line will run from the pump outlet to our new fuel filter. We've used a 37-degree flaring tool and AN tubes, nuts and adapters to connect to the fuel pump. The tubing, fittings, and tooling were all purchased from Summit Racing.
Fuel Line Sizing
The next major decision we were faced with was sizing the new fuel lines. These lines need to be sized based on the fuel requirements of the engine. The stock '65 fuel line is 5/16" diameter steel tubing. This size is not adequate for a high performance engine. In general terms, 3/8" line and AN6 fittings are good for around 400 Horsepower, which is our eventual goal. When comparing fuel lines, we must keep in mind that the capacity of a tube is proportional to the radius squared. Doing the math, a 3/8" line will carry 44% more fuel than 5/16". A larger ½" line will carry two and a half times as much fuel as a 5/16" line. A small increase in diameter makes a big difference in capacity.

Once the 3/8" size was determined the next choice we were faced with was what material to use. Our material choices included steel, aluminum, or special high pressure hose. Aluminum was the choice we made, as it is much easier to shape and form than steel yet is still very durable. Whatever the material choice is, the tubing must be capable of standing up to the maximum pressure the pump can deliver. If the return line becomes blocked or the fuel filter gets clogged, all or part of the fuel system will see that maximum pressure. This might be as much as 90 PSI at low flow. The fuel line must be rated to handle the pressure.

Another major decision that must be made when installing the new fuel lines is how and where to route the fuel lines to get from the tank to the engine compartment. This task was complicated in our case by the extra bracing Ford used under convertibles as well as the car's subframe connectors. Several routes were considered. Finally it was decided to remove the driveshaft so the lines could be clamped to the top of the transmission tunnel. The lines run forward to just aft of the shifter, where they elbow toward the passenger side of the car. While our old carburetor feed is on the driver's side, we are thinking ahead to an EFI future. Ford 5.0 engine's have the fuel inlet on the passenger side.


Here, a beautifully designed Makita 18V Li-ion cordless drill is used to cut a perfectly placed ¾" hole that is of course just too small to fit a 6AN tube nut through. The smart way to do this would have been to wait and make the second flare after the tube was inserted in the hole. Grrr!
There are a lot of different fuel filters available. This is one of the less expensive ones that will work with a high pressure system. This Trick Flow filter is set up for AN fittings so installation is simple. Disregard the rubber hose in this picture. It was part of the old fuel line that fed the mechanical pump and was later removed.

This picture is taken from the rear of the driveshaft tunnel, over the top of the exhaust with the driveshaft removed. Please ignore the welding clamp. It was just there holding a plug in the transmission so the red stuff wouldn't leak out. The picture shows four lines on the left. The bottom one is the shifter cable. The smaller line above that is the rear brake line. The two large lines above are our new fuel lines. They come forward from the tank then elbow and traverse above the tailshaft housing. Clamps were installed every 12 to 18 inches to support the new fuel lines.
The fuel lines were routed under the frame, exactly opposite of where the old stock line was on the driver's side, and up into the wheel well. Here, we've marked the holes we will make in the passenger side fender apron. AN bulkhead fittings can be used to make a super secure and clean installation into the engine compartment. Remember when ordering these that the bulkhead nuts are sold separately.

A tubing bender is being used to make the final bend in our new 3/8" aluminum return line.
The cut line is carefully marked, leaving about ¼" extra to make the 37-degree AN flare.

(Fuel Lines continued)

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In This Article...
FordMuscle friend Phil Ross continues his step-by-step instructions for installing a late-model style in-tank fuel pump in your classic Ford muscle car.

Also See:
In-Tank Fuel Pump Conversion PartI
Fitting Flare Up
Get In Line

Phil Ross is a FordMuscle contributor and goes by the handle "HoosierBuddy" on the FM Forums. He drives a 1965 Mustang Convertible which is in the process of receving a fuel injected 347 stroker.
Tanks Inc. Conversion Kit
Here we see all the goodies that come with the Tanks Inc. PA-4 Fuel Pump package. The kit includes a baffled assembly to protect against fuel slosh, inlet and return tubes, fittings, mounting hardware, a gasket, and a Walbro fuel pump rated at 250 liters per hour.

Fuel pumps need to be sized properly for the engine they will feed. In our case, we will be using the new pump to eventually supply a 347 stroker with EFI. The 250lph pump will support about 400 normally aspirated horsepower, EFI or carbureted as long as the proper fuel pressure regulator is utilized. Initially we are installing a return style fuel pressure regulator adjustable to around 5 pounds per square inch to the current carbureted 289 motor. We'll switch over to an EFI regulator once the 347 is in place.



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