How to Install AN Fittings to Hard Line 2024: Simplify every tough situation

Last Updated on September 13, 2022 by John Robinson

You might never get introduced to the complexity and intricacy of plumbing in the engine compartment of your vehicle unless you attempt it on your own. Your grinning and grunting giant of a vehicle is full of such amazing custom mechanical parts that stay hidden from the intriguing eye. If only you could visualize the role of every joint and bend in the working of your magical machine, you’d appreciate your car well. 

AN fittings are commonly found in high-performance vehicles and race cars. AN hoses are employed for the secured transfer of fuel oil, coolant, and hydraulic fluids within the engine. AN refers to Army-Navy as this special group was first developed as a standard set for flexible fuel connections that gained popularity during World War II. 

Typically employed in the aviation department, these high-quality fittings have now landed into the realm of race cars. A 37 degree flared fitting is employed to create a metal to metal seal. If you are thinking about customizing the hard lines inside your vehicle, get ready to witness some seriously wonderful tech. There are several types of lines to choose from, and several AN fittings to gleefully employ. No matter what addition you want to make to your stock system, there’ll be a different way to cut out the stock line.

The plumbing and the replumbing of your stock engine requires an in-depth understanding of the hydrodynamic principles that govern its functioning. Even the addition of an inline fuel filter would require you to install certain AN fittings to the hard line. Certain respectable committees approve the usage of all such fittings and couplings that allow the proper flow of liquids and gases within your engine. These include the NPT, JIC, BSP, and the SAE. 

How to Install aN Fittings to Hard Line

  • Understand the working of hardline Tubing

Hard-line tubing, contrary to their name, can be conveniently formed according to whichever requisite shape. They are easily utilized along with tube sleeves , tube nuts, compression adapters, and certain other hard line tools. Experts usually recommend stainless steel, aluminum hard line tubing, easy-form, or steel. 

How to Install an Fittings to Hard-Line

Aluminum tubing is very easy to form by hand and can be conveniently utilized for every other requirement. You can choose to employ it with hose ends, tube sleeves, tube nuts, or they can be flared according to your need. You can even weld an adapter at their ends if it serves your purpose

Compression adapters allow the junction and the transition between hardline tubing and AN plumbing. These are usually meant for low-pressure applications and do not require flaring tools. Note that you can re-use your compression style fittings with the help of compression olives.

All automotive applications typically employ steel tubing. This includes your brakes, transmission cooling lines, and even the fuel lines. It is recommended that you choose from zinc-plated steel and olive w/PVF coating. 

Tube nuts are employed in the transition zone between hardline tubing and AN fittings. A special 37-degree flaring tool is used to properly form the end of the tubing. Tube sleeves are also used in the transition zone with the help of a 37-degree flaring tool. 

  • Understand the role of AN fittings 

AN fittings are popularly used because of the relative strength and security they render to the plumbing in your powerful engine. They are way more reliable and dependable than the traditionally used push on nipples and hose clamps. Nothing compares to the strength rendered by their ultimate seal. 

Three types of AN fittings are commonly used on race cars and other vehicles that deem high performance. The type of AN fitting corresponds to the way it is connected to the hose. This factory defines them as crimp type, push lock, and reusable hose ends. Their installation is rendered further easy because of their further distinction as non-swivel and swivel types. 

  • Different AN fittings are differently installed

The installation of AN fittings to hard tubing is rather easy because of the specific distinction between different types of AN fittings.

  • Know about the installation of crimp fittings

Crimp AN fittings are rather expensive. That’s why you would never see them being used by small racing teams. They are usually built at places where a lot of hoses are made as well. This is because they require a special hydraulic press along with particular dies to appropriately crimp the collar on the ends of the hoses. 

Crimp style hose needs new crimp collars to be reused. Although, when properly crimped, they are considered as the utmost strong and dependable fittings. 

  • Know about the installation of reusable hose ends Know about the installation of reusable hose ends 

These are the most commonly employed AN fittings. Most small racing teams use these fittings as they are rather economical. This is essential because of their reusability. Also, it is easy to assemble and service them with the help of regular hand tools. 

Reusable hose ends consist of a two-part setup that holds the hose in place. They are commonly employed along with the braided hose. This could either be made out of stainless steel or nylon braid. Reusable hose ends are available in a variety of sizes, colors, and angles. 

Although they are heavier than other AN fittings, they are known to render trustworthy security to the fit. Also, their hose clamping method of installation is considered much more secure than push locks. 

You’ll first need to unthread the hose end sockets from the main body. Then you can insert the braided hose into the socket. For a proper assembly, the socket has to be threaded over the nipple so that the hose inner diameter is more than the taper. 

The specific shape and the features of this fitting serve to clamp the hose in one place and prevent any occurrence of leaks. Once this is done, the female nut ends can be tightened upon the corresponding male fitting. This will result in a complete seal on the tapered surface. 

  • Know about the installation of push locks

Push locks are also commonly utilized by small racing teams. Moreover, they are very easy to install. They are available as a single unit with a barbed end. Because these fittings lack the feature that prevents the braid from unraveling, push locks are typically employed along with coated hoses. 

The hose is forced over the surface of the barb and then sealed. The barb can hold the hose in place on its own. You can also employ an extra clamp for additional security. 

  • It is important to know about AN sizes 

While this may seem confusing at first, AN sizing are necessary knowledge for the best installation of AN fittings to hard lines. The AN size refers to the outer diameter of the hose. It is specified in increments of 1/16th of an inch. Once you get used to it, you’ll be able to judge the size of an AN fitting in a glance. 

Particular sizes of these fittings are commonly employed for specific functions. -3 AN fittings are employed in brake lines. -4 AN fittings are typically utilized in fuel hoses. -6 AN are used in fuel or coolant hoses and -8 AN are often utilized for coolant and oil. -10 and -12 size AN fittings are used on coolant and vent hoses. 

  • There are different types of AN hoses 

Even the AN hoses come in a variety of types. Different applications require different strengths of materials. These types are mainly attributed to the differences in temperature, fluid type, and pressure and abrasion resistance. The inner liner for hoses is generally made of rubber of chlorinated polyethylene or Teflon. 

This layer is followed by a layer of mesh braid or nylon or stainless steel. Some hoses also have a dual braided mesh. Some have a smooth outer covering. Each hose may be differently constructed to handle particular fluids, extreme pressures, or temperatures. 

Note that braided hoses provide the best abrasion resistance but are comparatively difficult to assemble. At the same time, stainless steel hoses are quite sturdy but they can rub against other components and wear them. This is also why braided nylon hoses have an inner stainless steel braid. The additional layer of nylon prevents this type of abrasion. These hoses are generally employed along with crimp and reusable AN fittings.

Push-lock fittings utilize hoses with smoother skins on the outside and braided mesh at the interior. The braided mesh provides sufficient strength and protects the inner liner. 


AN fittings are commonly employed in race cars and high-performance vehicles to render additional strength and security to hard lines.  Small racing teams generally employ reusable hose ends and push-lock AN fittings. Crimp AN fittings are typically used by more high-end racing teams because they require special tools for installation. These flexible fuel connectors are not only attractive, but they also avail boundless strength to the hard lines by creating a metal to metal seal. 

AN fittings are very reliable and quite popular in demand. For the best results, seek help from a professional. 

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John Robinson
John Robinson

Howdy! I’m John Robinson from Levittown, New York. I am a mechanical engineer for 15 years and already had an established car repair company. I developed a personal relationship with cars since I was a kid. I always love the sounds and smell emitted by a car or truck and even at construction machinery. Since then I have been married but my love for cars only grew.