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Special Delivery—Retrofitting a 30-year-old Fox Mustang with durable Aeromotive PTFE fuel hose

Posted By: Evan J. Smith
Special Delivery—Retrofitting a 30-year-old Fox Mustang with durable Aeromotive PTFE fuel hose
Written By Steve Baur
Photography by the author and courtesy of Aeromotive, Inc.
Fox Mustangs remain as popular as ever with both street and racing enthusiasts, and the aftermarket is still churning out part after part to support the platform. If you think about it, though, ‘90s-era Mustangs are over 30 years old, and not all of those aftermarket parts age so gracefully. Just like many of the body kits of the day, steel braided rubber fuel line doesn’t quite stand the test of time and when we came across a Mustang that was showing signs that the rubber lines were failing, Aeromotive’s PTFE fuel line was the answer.
Back in 1938, Dupont chemist Dr. Roy Plunkett was working with various gases related to refrigerants to develop something less toxic than what was currently being used, and Tetrafluoroethylene was one of those substances. Nothing came out after opening what was supposed to be a relatively full tank of it. A subsequent inspection of said tank revealed that the substance had polymerized all on its own into a solid, a waxy, slippery solid inside.
In its solid state, polytetrafluoroethylene is inert to nearly all chemicals, meaning it does not react with them. Dupont called the PTFE “Teflon” and trademarked the name in 1945, after which it has been used in a myriad of applications for decades, including frying pans, carpets, clothing, human implants, and of course, fuel hose. 
According to, PTFE is known to be the most slippery substance on earth and it is particularly adept at resisting harsh chemicals such as today’s internal combustion engine fuels.
As tough and durable as rubber can be, and as revolutionary as it is in its own right, it does have a life cycle. Whether you are hitting it with UV rays from the sun like your vehicle’s tires are exposed to or fighting to contain ethanol/blended gasoline like the kind that fuel lines must deal with in this day and age, the life expectancy of rubber is affected. When rubber is exposed to these things for extended periods, it can degrade and eventually fail.
That said, stainless steel braided rubber fuel line is relatively inexpensive, easily obtained, and relatively easy to install. The cost savings, however, does come at the cost of longevity, so that should be considered before deciding which type of hose to use in your build.
According to Aeromotive’s Brett Clow, further modifications had to be made to PTFE to allow it to be used in fuel lines.
“Early PTFE line you could use in a variety of things, but not in a fuel system,” Clow said. “The line we use is carbonized or graphite-impregnated so it can ground itself to the fitting, which is usually connected to something in the fuel system that is grounded,” he said. “In a flowing system where you have a velocity of flow in a tube, static electricity can build up and you can build a charge within it that can perforate the tube and ground to the stainless braid. The carbonization provides a conductive characteristic to the PTFE.”
Once that process was implemented, PTFE could be used with fuels and the PTFE line offers two main features or selling points.
“It’s not going to break down or come apart in time, which is what happens with rubber products with today’s fuel blends,” Clow stated. “The ethanol content extracts the oils in the rubber, and as they are drawn out, the rubber hardens and can microfracture and begin to leak or come apart. One of the big things is permeation. A rubber hose has a porous construction and vapor can escape. PTFE won’t allow that. If you’re going to build something you want to keep, we would guide you towards PTFE because of these benefits.”
The other main benefit of using PTFE fuel line is its reduced size.
“It’s much smaller OD than rubber line because its wall thickness is much smaller,” Clow pointed out. “It fits in the car better—two lines together take up less room. It’s bendable, but not floppy. It’s deceptive in size as many people think we sent them a smaller hose because of its smaller OD, but the ID is larger.”
With a much different physical size and material construction, it shouldn’t come as a surprise that the PTFE fuel line requires a different type of fitting to make connections.
“A hose end for PTFE uses a typical compression type of fitting that uses an olive or ferrule that compresses the tube between the olive and the nipple of the fitting,” Clow noted.
It’s a minor change to the hose/fitting assembly that is easy to do and doesn’t add much time to your installation.
The rubber fuel lines on our subject vehicle had begun to fall apart and particles started clogging up the fuel filter. Cleaning the fuel injectors revealed that they, too, were becoming affected by the breakdown of the rubber fuel lines, so we contacted Aeromotive and ordered new PTFE fuel lines and fittings to both replace the failing fuel system components and to update the look of the engine bay, which was still utilizing “vintage” parts from the ‘90s that have fallen out of favor style-wise.

Whether you are building new or replacing outdated parts in your fuel system, Aeromotive has everything you could ever want or need. We upgraded the fuel lines, fittings, fuel pressure regulator, and fuel rails to bring this supercharged Mustang to current standards.

Aeromotive’s PTFE stainless steel braided fuel hose is available with the traditional stainless steel braided cover for strength and protection, and the company also offers an optional black poly jacketed version when you want to black out your fuel lines. The PTFE hose is available in AN -06, -08, -10, and -12 sizes and ships in pre-cut lengths of 4-, 8-, 12-, and 16-feet. It’s also rated at 1,200 psi of continuous working pressure.

This 383ci supercharged Windsor powerplant has made over 630 rear-wheel horsepower, but it’s barely been running lately due to the aging rubber fuel lines that are falling apart. While we are replacing those, we wanted to update the engine bay and replace the red and blue components with modern black-colored versions, and the PTFE hose requires different fittings regardless.

This particular vehicle has already been upgraded with several Aeromotive products such as the fuel pressure regulator and now-discontinued sumped fuel tank. We opted to mount the new fuel pressure regulator (PN 13303) in the same location as the previous one as we felt there was no improvement to be made by changing the hose routing.

Commonly seen in the ’90s, this fuel system utilized a dead-headed driver-side fuel rail with the passenger side returning the unused fuel to the regulator. We planned to change that to a two-in, two-out setup.

The supply line can be seen here making the U-turn to the left and toward the firewall, while the return line routes forward to the regulator. We didn’t change any routing here, but the smaller PTFE line will certainly provide more room with its smaller size.

The aforementioned supply line splits at the firewall to feed the two fuel rails, which are being replaced with Trick Flow by Aeromotive fuel rails (PN 14171) in a black anodized finish.

We began removing the fuel lines and then separated them. The return line was the first one to be replaced, and since the routing was already optimal, it was kept the same.

Here you can see the now-discontinued Aeromotive Stealth fuel tank — the company has since gone to factory-style tanks with a top-mount, drop-in design rather than the rear sump. That said, the current tank was functionally in good condition and we appreciated its exposed mechanical look, so we opted to re-use it and just replaced the return line on the right, and the supply line on the left, which snakes around and up to the fuel filter mounted above the rear axle.

When you receive the PTFE fuel line, you’ll need to make a clean cut so the hose seats into the ferrule properly. Here you can see it has been deformed due to the manual cutters that are used.

The best tool for cutting PTFE line is a chop saw with a carbide blade. It will hold the line firmly and squarely, the latter of which is difficult to obtain using a cut-off wheel.

Here is the ferrule or olive that must be pressed into the line. You do not need any sort of mechanical press, just a firm surface and a little elbow grease.

First, slip on the nut for the fitting and then spread the braided stainless steel so the ferrule with slide inside it. The PTFE liner will slide inside the ferrule.

The PTFE liner will bottom out in the ferrule, just be sure not to use too much force, as you can deform the liner and push it past the end, which will then require you to start over with another clean cut.

You can probably put the fittings together with a pair of AN wrenches, but using soft grips like these for a bench vise will make it much easier. 

With the fitting nut in the soft grips, slide the fitting into the ferrule until it bottoms out, and then push the hose through the nut until the fitting meets the nut. 

Apply some slight pressure to the fitting while ensuring it engages the threads squarely, and turn the fitting to start threading it in. Then use an AN wrench to tighten the fitting. It does not have to bottom out into the nut, so if you meet too much resistance before then, it’s likely safe to stop at that point.

With the new return line completed, we started on the supply line.
We replaced the previous Aeromotive fuel pressure regulator with this new one, which received a return line from each fuel rail.

While the routing is a bit tricky on the small-block Fords, their accessory drive, and having a supercharger mounted in the way as well, we were able to run the two -6 return lines under the blower and over to the regulator. The updated fuel rails and regulator provided us with the needed appearance upgrade, and this Mustang’s fuel system will likely outlive the engine and be ready for the next one thanks to the Aeromotive PTFE fuel hose.
Aeromotive, Inc.
(913) 647-7300

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