Making Custom Braided Fuel Lines With AN Fittings

Making your own fuel lines may sound difficult, or even scary, but it’s actually pretty easy and fairly safe. Whether you need a new fuel line as a part of a restoration project, or are trying to prep for a larger turbo charger, braided lines are worth considering. While not as strong as solid steel or aluminum lines, braided lines offer more strength than standard rubber fuel lines with the same flexibility. That means that you can use it in places that have to compensate for engine movement, such as supply and return lines on your fuel rail. The added strength helps support higher fuel pressures that are common in high performance engines, particularly turbo and super charged engines.

Right now, I’m getting ready to install an AFPR (Adjustable Fuel Pressure Regulator) I picked up in a classified ad over at DSMTuners. The factory regulator mounts directly to the fuel rail. To remove it and upgrade to an adjustable one, we’ll need to create a new fuel line connecting the new AFPR mounted on the firewall to the existing fuel rail mounted between the head and intake manifold. To do this, we’ll replace the stock FPR with an adapter on the rail which adapts the rail for -6AN fittings. Then, we’ll mount another -6AN connector onto the new AFPR. To connect the two, we’ll need to create a -6AN fuel line long enough to reach from the fuel line to the spot on the firewall where we’ll mount the AFPR. For those unfamiliar with the term AN, it stands for ARMY/NAVY and is a sizing standard developed by armed forces. It’s commonly used in fuel, transmission, and vacuum lines in performance applications as opposed to NPT sizes, which are common in both air tools and factory line sizes.

Making a custom fuel line is pretty simple. We just need a a couple things:
  1. Some tape – This will keep the hose end from fraying when we cut it
  2. Something to cut the line with (preferably a dremel or other high speed cutter for stainless braiding, but tin snips will do for nylon braiding)
  3. A tape measure
  4. 2 -6AN hose ends – I used one straight hose end and one 90 degree end
  5. A –6AN wrench – I used a crescent wrench, but that was a mistake as you’ll see in the video
  6. A bench mounted vise
  7. Aluminum vise jaw pads – I made some with angled aluminum I had laying around, but it’s cheaper to just buy them if you don’t already have scrap aluminum to use
  8. 6AN Hose
First, use the tape measure to determine how much hose you need and wrap where you’ll cut with the tape.  The tape will prevent the hose from becoming too frayed while you cut it. This will make it easier to fit the hose end’s cap over the cut edge of the hose. Cut through the tape and remove it from the end of the hose.
Once you have the hose cut to the length you want it (I made mine 24 inches, but I think 18 would have been sufficient too), separate the two pieces of one of the hose ends and place the cap piece into the bench vise between the aluminum jaw pads.  Insert the end of the hose into the cap and push it until it seats as into the cap where the diameter reduces slightly.
Once the cap is fully seated on the end of the hose, insert the shanked piece of the hose end into the cap piece and begin threading it by hand. Be careful not to cross thread the hose end pieces together as these pieces are very easy to break. It’s best to take your time and go slow. Start threading by hand, and use the AN wrench to finish tightening it. Using an aluminum AN wrench rather than a standard wrench will prevent damaging the anodized coating of the AN fittings. As the shank threads into the cap, it will push on the inside of the hose, forcing it to expand into the walls of the cap. This forms a tight seal, which combined with the nylon reinforcement on the hose result in a stronger hose than a factory push on type which is less likely to blow off.

Once the shank end is fully threaded onto the capping end, you are finished with that end of the hose. Repeat the process using your other fitting on the other end of the hose.

Here’s a video I made of the process with my buddy, Jake Penner, doing the camera work.

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