AN fittings offer much more than just fine looks—they provide the perfect seal necessary for reliable and safe plumbing throughout the vehicle. Upfront, you should know that setting up your vehicle to run AN fittings is a hefty investment. It’s definitely worthwhile, but there are still some things you will want to know before dumping money into a more reliable and aesthetically attractive system.
Making Sense of Those Numbers
Unless you’ve had a decent amount of exposure to AN fittings, looking through your options can be puzzling, as suppliers tend to lean on preliminary knowledge. This means, a bunch of new terms might be dumped in your lap.
Sure, you can figure out angle values and thread type (male or female) but the confusion starts settling in when negative numbers start showing up. So, what do these numbers mean?
Well, let’s start with where they come from. AN means Army/Navy, as these fittings and their designations were actually put to use as far back as WWII. It’s thanks to a joint agreement between the Army and Navy that we actually have standardized sizing.
The numbers used for sizing refer to the outside diameters of the tubing in 1/16” increments. So, for example, a -2 fitting is equivalent to 2/16 of an inch or 1/8”. That means, a -3 fitting equals 3/16”, a -4 equals 4/16” (i.e. 1/4”) and so on. Since we know that different tubing and hoses have different wall thicknesses, we can deduce that this system does not tell us what the inside diameter is. However, each AN size has its own standard thread size, which you can find in a handy chart like the one below.
Furthermore, these units are tolerance sensitive and each manufacturer’s specs will vary. Because of this, it’s important that you not only match sizes, but also use fittings from the same manufacturer. Otherwise, you can end up with a leaky connection.
It is also important to know that AN sizing and NTP sizing are different, so an AN fitting won’t work with an NTP fitting. Additionally, NTP fittings use a tapered thread while AN are non-tapered. Basically, always attach like with like. Mixing fittings will result in leaks.
Why Make the Upgrade?
This tech was introduced in WWII and since then, AN fittings can be found in pretty much any type of vehicle. The history is undoubtedly interesting but if you have to relearn the wheel, you may be asking “why bother?”
“Peopleuse AN fittingsbecause they look cool and provide a securefittingthat seals hoses better than traditional push-on nipples and hose clamps,” explains Kanga Motorsports. “They form a serviceable connection that provides a reliable seal.”
Great performance, great looks, and great history. All of these reasons have earned AN fittings a spot in thousands of hotrods, muscle cars, and even imports. It’s also worth noting thatsome high-performance upgrades designate using these fittings, like fuel pumps. But even if you just prefer the look, you can install them on virtually any system.
Keep in mind, different fittings are used for different applications. Adapter fittings are designed to mate an AN fitting to the operating system but can also be introduced intermittently throughout the hose for teeing off. Barbed fittings are designed to fit into rubber hose. There are also compression fittings used to adapt a hard line to an AN fitting.
As mentioned, this upgrade comes at a cost, but there are a number of reliable suppliers on the market to choose from—just beware of those that are sketchy cheap. Remember, these are tolerance sensitive units and cheaping out can lead to a nightmare’s worth of leaks.
Still, you may just need to plumb up your fuel system and don’t exactly intend to go broke doing it. Lucky for you, SpeedFX—the brand that’s been knocking it out of the park with affordable, reliable speed parts—has begun its descent into the world of AN fittings. So, if you’re looking for budget-friendly quality, I recommend starting there.
Fitting & Hose Selection Is a Balancing Act
While the AN fittings themselves are the most attractive part of the system, the selection should be made based on the type of hose you’ll need. And, it goes without saying, that the application the hose will be matched to will have a lot to do with selection.
If the hose is to exist on a specific operating system, you need to make sure that it’s up to snuff. Additionally, if you’ll be racing, you will also need to make sure the sanctioning body approves of the hoses and fittings used. A fantastic supplier to check out is Aeroquip Performance. The brand offersa wide variety of hose and fitting options that are designed to be used with fuel, high-pressure, or even AC systems. Plus, Aeroquip has 75 years of experience under its beltand these guys are the number one choice of racing enthusiasts around the world.
Among Aeroquip’s offerings, you’ll also find PTFE fittings and hoses. More commonly known by the trademarked name Teflon, PTFE hoses are lined, which allows them to be particularly resistant to corrosive chemicals. “When pressures and temperatures are high, this is your hose of choice,” says Aeroquip. “No other hose product offers the performance and efficiency of this stainless braided, Teflon inner tube for superior fluid compatibility.”
Mostly intended for methanol and ethanol, PTFE can also be used with pump gas applications. Just remember, if you’re building a vehicle and need PTFE hose, you will also need matching PTFE fittings from the same manufacturer. While these are similar to a traditional AN fitting, they use a compression fitting to seal. This requires some special care as it needs to be applied to the hose by removing the exterior covering.
Not Done Yet
So if PTFE fittings require special installation procedures, what does it take to install standard AN fittings? Do you need specialty tools? Can you even do this on your own? While this overview hopefully has helped you to learn a little more about what AN fittings are, there’s still a lot more to know. Check back soon, as we’ll continue this conversation and help you get properly fitted under that hood.
