Making Connections: Adapting Factory Quick Disconnect Fuel Lines To AN Hose Ends (2024)

Words And Photos: Jeff Smith

It’s a brave new world out there. By now everybody is familiar with the new family of engines – GM’s LS series, Ford’s Mod motors, and Chrysler’s impressive Hemi engines. Engine swaps using these latest generation engines are becoming increasingly popular and with that come issues with the little things – like connecting fuel lines to that new breed of factory fittings. The OE’s have created a whole new line of quick-disconnect (QD) fuel lines that have become the new standard of fuel transfer fittings. This has come about partly because the installation is literally a snap. But just because it’s easier for that guy on the production line to install, doesn’t necessarily make it easier for gear heads and engine swappers to make these connectors work for us.

To make engine swaps and working on these engines a little easier, we’ve assembled a simple guide for making, breaking, and reusing these connections. While the assembly is easy, the disassembly is also a snap – if you have the right tool.

Before we get into the specifics, it might be useful to know why the OE’s decided to invest in QD’s and plastic fuel line. The overriding issue wasn’t pressure – even though most new engines demand 58 psi fuel pressure. The bigger issue was emissions. All rubber fuel lines allow fuel vapors to escape and one of the emission standards subjects vehicles to what is called a shed test where the vehicle is parked for a given amount of time and all engine-off emissions car are recorded. If you’ve ever smelled raw gasoline vapors after parking your hot rod in the garage after a quick run to the Dairy Queen, then you’ve experienced a backyard version of the shed test.

To minimize escaping fuel vapors, the OE’s changed to a plastic-like PTFE (polytetrafluoroethylene, if you must know) material for fuel hoses. This new hose also demanded a brand new line of factory connectors commonly referred to as quick-disconnects – QDs. Now that you have the full background skinny, we can get into the details of how to adapt these rascals to a more familiar -6 or -8 AN fuel line.
One important caveat that deserves mention is that these QD fittings must be installed properly. Since all late model engine run at such high fuel pressures, leaks at this pressure are intolerable. These QD fittings are designed so that leaks will not occur if the fittings are installed correctly. So spend a little time with these adapter fittings to ensure there are no leaks. Your hot rod is too important to take changes with the fuel delivery system.

GM

There is probably not a more popular engine swap on the planet right now than the LS engine swap. We’re talking cars, trucks, boats, off-road vehicles, and more than a few aircraft. The majority of these swaps involve stuffing a stock or near-stock engine in an older car. The beauty of the popularity of the LS engine is that many companies have products to make the connection as easy as possible between these new generation fuel fittings and AN hoses.

The most common LS factory connectors use a male steel rail that is attached with a female o-ring connector that just clicks into place. To adapt these male fuel lines, you will first have to remove the existing factory connection. To do this requires a simple yet essential plastic QD tool available almost universally. One of the more common ones is a Lyle combination tool. You can find this tool at many auto parts stores or on Amazon for roughly $15. We also found an aluminum multi-size scissor-like tool for $6 at Summit Racing if you’d rather go that route. There is a specific tool for each size fuel line – in the case of the Lyle tool, the blue one is for the 5/16-inch lines. Slip the tool inside the female connector and it will unlatch the connector and then you just pull them apart. There’s no easy way to do this properly without the tool.

Once the lines are separated you now have plenty of options The most common application for engine swapping is to adapt a -6 AN fuel line to the existing LS fuel rail. Aeromotive, Earl’s, Russell’s and others make a simple adapter that will do this job for you. These fittings are somewhat complex which is why they sell for as much as $38 but for this price you do get simplicity. The Aeromotive fitting, for example, makes a solid connection to the fuel rail and on the other end uses a female AN-8 fitting that will connect right to any braided steel hose. You will need two of these fittings – one for the high pressure fuel supply line that is generally a 3/8-inch fitting and also a smaller, 5/16-inch line for the fuel return line.

For more aggressive engine applications, it might be a good idea to step up to a complete fuel rail kit which Aeromotive also offers. This kit consists of a pair of billet aluminum fuel rails designed to bolt onto specific applications such as the ’97 – ’04 LS1/LS6 engines, all the LS3/L76 applications, and even the LS7. The kits also include the specific adapters as well as fittings and a pressure regulator. This kit would be especially useful on high output engines where greater fuel flow is anticipated.

Another installation option for the GM guys is to skip the adapters and use a factory style QD connector on the end of a length of PTFE hose supplied by TechAFX. This company offers a factory-like fuel hose that is impervious to all kinds of fuel including E85 and methanol. The company can install a factory-like swedged QD fitting on a length PTFE line. TechAFX also sells AN hose ends for the other end of the hose to connect to a Y-fitting or other connection. The advantage of the PTFE fuel line is it offers near-permanent life expectancy. The problem with rubber fuel lines such as stainless or cloth covered hose is that current-blend gasolines with ethanol tend to dry out regular rubber fuel hose from the inside, reducing the hose’s life expectancy. Recent changes in rubber fuel line chemistry have extended the life of most quality hoses but all rubber hoses have a finite lifespan. The most common cause of failure is when the rubber hose becomes brittle and cracks.

Ford

Blue Oval fittings operate on a very similar basis to the GM and Chrysler QD fittings and often the same tools can be used to separate the female end from the male connector. Aeromotive has a wide assortment of adapter fittings for the Fords including a couple of T-shaped adapters that will pull two male -8 male AN connectors off either a ½-inch or 3/8-inch Ford fuel line. Aeromotive also offers the popular male 3/8-inch spring lock that feeds to a male AN -6 connector. Several of these fittings also come with a 1/8-inch female NPT gauge port which is a perfect place for a fuel pressure tap.

As with the GM lineup, Aeromotive also offers fuel rail kits for a multitude of Ford applications way too numerous to mention here but spanning ’96-’04 4.6L Mustangs to 5.0L Mustangs, 5.4L trucks, the GT500 Mustang and even the new ’11-’13 Coyote 4-valve 5.0L versions.

Chrysler

The simple version is that the Chrysler fittings appear to be very similar to the GM versions so that converting a Mopar late model hemi over to AN fuel lines is incredibly simple and for once doesn’t cost any more than the same parts for a GM or a Ford! That alone is cause for celebration. And Aeromotive has you covered if you’re contemplating a big power conversion for a Gen III 5.7 or 6.1L Hemi and there are even V10 Viper kits.

ORB

While we’re on the subject of fittings, many of the female QD adapter fittings are designated as ORB fittings. We recently read a review of one of Aeromotive’s female fittings on a forum where the reviewer returned the fitting because he complained that the female part of the fitting was “tapped too deep” to work with his pipe thread fitting. The reason for his frustration was that he was using the wrong fitting. The ORB designation stands for O-Ring Boss where the female portion of the fitting is designed to use the standard AN thread pitch and seal against leaks with a simple o-ring.

ORB fittings are becoming increasingly popular as the fitting of choice for aftermarket fuel pump and fuel filter connections. These components use specific ORB fittings that come with an o-ring recessed into the base of the male threads that will seal to a matching ORB fitting or component. Most AN companies sell these fittings but not all ORB fittings come with the o-ring. Aeromotive fittings do come o-ring-equipped and rather than a butyl rubber o-ring, Aeromotive uses Viton as it is impervious to all the different fuels and offers a much longer life. In addition, you can purchase a package of Viton seals separately from Aeromotive if you need to replace one that has been damaged or if you want to upgrade a different ORB fitting.

Late model engine swaps will continue to be the hot topic for years to come. Sometimes the new technology can be intimidating. But with the right adapter fittings and a little common sense, you can quickly overcome these minor hurtles and go on to bigger and more powerful adventures.

Parts List

Sources

Aeromotive
aeromotiveinc.com

Holley Performance Products (Earl’s)
holley.com

Jiffy-tite
jiffy-titemotorsports.com

Edelbrock (Russell)
edelbrock.com

TechAFX
techafx.com