Relocating and Plumbing the F100’s Fuel System

Regular readers are aware of Project F-Word’s rapid progress as things have rapidly escalated on our 1969 F100 project truck since it was disassembled and rebuilt from the ground up. Now that the chassis and suspension are mostly resolved, we have one Ford performance Gen 3, 5.0-liter Coyote Aluminator (more on that to install) and a Tremec T56 Magnum 6-speed from Silver Sport in. This time, we’re going to redesign and build the fuel system to feed that coyote.

The first step in moving the gas tank is to remove it (obviously – this truck no longer had the supply tank, which saves us that step), then rip the bed off the frame. It’s just a few bolts that hold the bed in place. Support the frame with jack stands, of course!

In case you didn’t know, trucks from the 1960s had their fuel tank in the cab, behind the seat; Chevy and Ford both. Of course, this isn’t the safest location to put it – you’re essentially driving a bomb with all the fuel always right behind you. Therefore, it is common for owners of these trucks to move the tanks to the rear part of the truck under the bed, where the factories eventually moved them.

We have found that Holley has a nice “wish list” feature of their website where you can specify and order all the parts you need in one step. So we went hunting.

In the case of our project truck, which was supposed to make a lot of steam with the hot Coyote engine under the hood, we wanted to do just that – take the tank away from the driver and put it under the bed. Turns out a 1969-1970 Mustang gas tank fits almost perfectly between the frame rails with just a little effort. So that’s what we did, mostly using Holley‘s parts on the way.

We started with the 400 l / h Sniper EFI fuel tank system capable of supporting up to 750 horsepower. We have added the renowned HydraMat Fuel Mat for good measure to avoid starvation, although the included tank has a 4.3 liter internal baffle. The fuel system comes complete with the galvanized and powder coated tank, 400 lph in-tank fuel pump, hanger and transmission unit so all you have to do is guide it to your fuel rails and secure it.

Then remove the rear bumper and frame brackets to gain better access to the rear crossmember, which must be moved to make room for the gas tank. (You will notice that we have completely stripped the truck at this point).

We wanted to accomplish that task, starting with removing the cargo box and rear bumper / brackets to allow us to move the center frame crossmember back enough to fit the Mustang tank. We then supported the rear frame with jack stands to make it sturdy.

We then ordered all parts and fuel system hose, fittings and the like online from Holley’s wish list function, and put it all together. This is a great feature on Holley’s site – we use it all the time. Now that we have a complete, relocated (and safer!) Fuel system to feed that hungry Coyote, this pup is almost ready to hit the road and tear up a few autocrosses!

The parts list

  • Sniper EFI fuel tank system (400 l / h) for 1969-1970 Ford Mustang (Part No. 19-417)
  • Hydramat (3 × 8) 11mm center exhaust with 6 locking pins (Part No. 16-124)
  • Earls 100 gph billet aluminum fuel filter – 10 micron, – 6 AN female inlet and outlet (Part No. 230606ERL)
  • Earls -6 AN bulkhead nut (Part # AT592406ERL)
  • Earls -6 AN Male to 3/4 ″ -16 (Part # AT985068ERL)
  • Earls -6 AN Male to 9/16 ″ -18 (Part # AT985006ERL)
  • Earls 2 Piece Aluminum Adjustable AN Wrench Set (Part No. 230351ERL)
  • Earls 90 degree -6 AN bulkhead (Part # AT983306ERL)
  • Earls Flame Guard Insulation, 10 Feet (Part No. 571008ERL)
  • Earls fuel filter mounting brackets (Part No. 230622ERL)
  • Earls hose and hose separator (Part No. 167509ERL)
  • Earls HP billet EFI by-pass fuel pressure regulator (P / N 12846ERL)
  • Earls OE Fuel Line EFI Quick Coupler -6 to 3/8 (Part # AT992066ERL)
  • Earls pipe sealant (Part # D024ERL)
  • Earls pressure gauge (Part No. 100187ERL)
  • Earls straight male AN -6 to 1/4 ″ (Part # AT981606ERL)
  • Earls UltraPro hose end -6 AN (part # 620106ERL)
  • Earls UltraPro hose end -6 AN 120 degree angled hose end (Part No. 621206ERL)
  • Earls UltraPro hose end -6 AN 45-degree forged hose end (Part No. 624506ERL)
  • Earls UltraPro hose end -6 AN 90 degree forged hose end (Part No. 629006ERL)
  • Earls UltraPro hose end -6 AN 90 degree angled hose end (Part No. 629106ERL)
  • Earls UltraPro Check Valve – 6AN Male – Stainless Steel Hinged Door with Viton Seal (Part No. 253006ERL)
  • Earls UltraPro Series Tubing, 10m Long Double Helix PTFE Ribbed Tubing (Part No. 693306ERL)
  • Replacement Bolt-On Fill Neck and Aluminum Cap Kit (Part No. 19-166)

Cutting, grinding, welding

To remove the crossbar, we used a grinder, chisel and punch to knock off the rivets that held it in place. Then move the crossmember to the rear part of the frame and turn it upside down so that the “hump” points down to the ground. Read also : Plumber: Looking to install a basic bidet seat – Sioux City Journal. Finally, align and enlarge the back bed bolt holes to make sure they fit the bed bolts. These are located on the top of the frame.

Now is the time to mock the Holley Sniper tank in the location we chose. After seeing it slide almost all the way in, we took some general width measurements and removed about half an inch from the bottom portion of the frame rail on each side. This is to allow the tank to fit flush against the rail and in the desired position. (If the tank is not equipped with the pump, fill and shipping unit, make sure to tape the holes so that nothing gets into your clean and new tank).

The tank is now prepared and can be pushed into position. We were able to get the tank straps bent and put in place. We bought universal tires from Tanks Inc., and insulator rubber from Summit Racing, both of which were very easy to work with. The belts are galvanized for corrosion resistance and long life. There is a crossbar directly behind the axle that serves as a perfect place to secure the front of the belt, and the passenger side belts had a few holes drilled large enough for the bolts and locknuts we wanted to use. We put the bolts through the crossbar and welded them in place so they wouldn’t turn, making them easy on and off.

Since we have plans to autocross this truck, we went a bit overboard by adding extra support. The gas tank has an extra lip beyond the weld where the two halves of the tank (top and bottom) are welded together. We drilled two holes through the lip of the tank and through the frame, and used two smaller bolts to attach the sides of the tank directly to the frame. To make sure there was an easy way to keep the nuts from turning, we used a ½ inch wide piece of steel and welded two nuts to use in the frame from the top. (we didn’t want to weld these bolts through the frame as it might be difficult to get them all lined up later.

In with the new

We designed and used all Earl’s Performance lines for the entire fuel system. As you can see from the pictures, we have used -6AN fittings, piping, regulator, filter, NPT sealant, wrenches and more. We used -6 AN to 1/4 ″ NPT to match the AN line to the Holley Sniper Fuel Hat. Scroll up for a complete parts list including Holley’s 1969-1970 Mustang fuel tank system.

It’s important to mention that we swapped the OE fuel sock for the Holley HydraMat direct replacement sock to ensure we keep the fuel supply to the 400 lph pump on hard turns. The HydraMat is like a sponge for fuel: it sucks it up from where it touches the fuel and keeps the pump filled.

Then we had to decide where to put the regulator, we wanted to put it somewhere that looked good but was usable and would allow us to access the gauge in case we needed to diagnose something with the truck. That is why it was decided to mount the controller directly behind the motor on the firewall. We have analyzed the firewall and installed some threadserts to mount it.

We then decided where to mount the fuel filter. We first wanted to mount all the hard parts that are in a fixed position and then run the lines, and found a nice spot between the suspension in the frame rail that would be easy to maintain.

The check valve goes on the inlet side of the filter, as seen here. It’s the silvery little part on the right side of the Earls filter).

We wanted to keep all the lines within the frame rail so as not to compromise them, so we ran them through the rear crossmember to the Earl’s fuel filter, then attached them to the frame with Earl’s hose and hose separators. These are excellent clamps that made mounting and securing the lines easy.

This is where we had to get creative – we approached the center pipe and long pipe ends section of the truck and really wanted to keep the lines away from the hot head pieces. We ended up using Earl’s bulkhead fittings to pass through the frame to transfer the lines to the top and outside of the frame for the last few yards of the run. In this photo you can see the transition from the bulkhead and then again the use of the Earl’s Hose and Line separators. We used Earl’s Flame Guard insulation to make sure any heat around that part of the line wouldn’t be a problem and keep the fuel nice and cool. We have used this product with great success in the past with our brake and clutch lines.

From here it was just a matter of measuring and assembling the remaining pipes to make all connections for the return pipe. To make the final connection to the OE fuel rail, we used the Earls OE fuel line EFZI quick disconnect fitting that converts the OE OE fitting on the fuel rail to 6AN.

Until next time

In the next installment, we’ll take a closer look at the Gen 3 Aluminator installation. And we also have some steering upgrades to our modern suspension… not to mention everything else to get this rusty old farm truck into combat form. Stay with us!

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