Mark Houlahan
Tech Editor, Mustang Monthly
January 27, 2014

Stainless Braid Rubber Hose

Moving on to the more traditional stainless braid style of AN hose you'll see there are a few more steps involved in making a complete hose assembly. The stainless braid itself makes the hose assembly a bit trickier, but the stainless braid look is what most people want, plus the braid is what protects the hose and gives the hose its strength. Traditional stainless braid is the most common, but we're seeing some hose companies offer a dark gray or black stainless covering now as well if you're looking for something a bit on the modern or OE side for a late-model engine swap for example. You'll find the broadest applications for fuel, oil, and more in the stainless braid hose, as well as the largest offerings in dash sizes too.

14. Once you’ve determined the length of your AN hose routing, the end must be given a clean cut (or the excess hose cut from the run length). As mentioned in our opening text, a high-speed cut-off wheel does a great job, though many use AN hose shears or even a sharp chisel and hammer.
15. Push the freshly cut hose end into the AN hose fitting socket with a counterclockwise turning motion until the hose end seats against the stop inside the socket as seen here. Getting all of the wire braid inserted is often the hardest part (and where everyone pokes their fingers). Stray wire strands can often be clipped with cutters if you only have one or two strands giving you trouble.
16. Lubricate the hose nipple and threads on the AN fitting using assembly lube or a light oil. This will help start the nipple into the opening of the rubber hose and prevent galling the threads on aluminum fittings
17. Use a piece of tape at the base of the AN socket to act as an indicator and then thread the AN fitting into the socket. Soft jaws in a vice can be used to secure the socket or you can simply use the age-old “two wrench method” of threading the fittings together. The tape applied at the base of the socket is used to verify the hose did not push out of the socket as the AN fitting was threaded in. If the tape line has moved, you’ll need to disassemble the AN fitting and try again. You want the fitting and socket to be within a 1⁄16-inch or closer.

PTFE Lined AN Hose

For high pressure applications (or if you're looking to save weight for some compatible fluid line runs), a PTFE (Teflon) hose with stainless braid is the answer. This hose is a little different in its assembly and we feel it can be the trickiest of the three AN hose types discussed here. The PTFE hose requires a special three-piece fitting (standard AN hose fittings are just two). The three piece fitting is used to give the PTFE hose the support it needs to seal at the fitting. The thin, flexible tubing otherwise would not seal (similar to a compression fitting for the plastic or copper tubing used on the water line for your refrigerator).

18. PTFE AN hose requires special three-piece fittings. The fitting is made up of a socket, olive, and nipple, shown here from left to right.
19. As with standard rubber-based stainless braid AN hose, you will have to determine your hose length and then mark, tape, and cut the hose accordingly. Once you’ve cut your PTFE hose to length, and before you remove the extra tape from the cut end, slip the socket end of the fitting over the stainless braid, ensuring the threaded end faces the cut end of the hose.
20. To install the olive, you have to remove the remaining tape that secured the stainless braid during cutting, carefully spread the braid open and away from the PTFE hose, and then press the olive over the end of the PTFE hose until it is seated squarely into the olive. Pushing the hose itself into the olive, supported against a block of wood is a good option.
21. The PTFE hose requires seating into the ribs found inside the olive. While some manufacturers state the nipple portion of the AN fitting can be used for this step, we prefer to use a tapered punch gently pushed into the PTFE hose to do the job.
22. Once the PTFE hose is seated to the olive, the nipple of the AN fitting can be lubricated and inserted into the hose until the olive seats against the base of the fitting, as seen here. Lubricate the threads of the AN fitting and thread the socket onto the fitting by hand. Finally, tighten with the proper wrench until you have 1⁄16-inch or less gap between the fitting and the socket

AN Fitting Specifications

While the complete range of AN fittings is from -2 to -32, the most commonly used sizes for automotive use are -3 to -24. Generally you will find -3 used for brake hoses, -4 used for nitrous system lines; and -6, -8, and -10 are most commonly found in fuel systems. The larger AN sizes are often only found in cooling system hoses and can be quite expensive by the foot, not to mention the cost of having the radiator, water pump and heater inlet/outlet converted to AN thread via adapters or welding new fittings in place.

AN Size Tube OD/Hose ID Thread Size Pipe Thread Size Std. Wrench Size
-3 3⁄16-inch 3⁄8-24 SAE 1⁄8-27 NPT N/A
-4 ¼-inch 7⁄16-20 SAE ¼-18 NPT 9⁄16-inch
-6 3⁄8-inch 9⁄16-18 SAE 3⁄8-18 NPT 11⁄16-inch
-8 ½-inch ¾-16 SAE ½-14 NPT 7⁄8-inch
-10 5⁄8-inch 7⁄8-14 SAE N/A 1-inch
-12 ¾-inch 11⁄16-12 SAE ¾-14 1¼-inch
-16 1-inch 15⁄16-12 SAE N/A 1½-inch
-20 1¼-inch 15⁄8-12 SAE N/A N/A
-24 1½-inch 17⁄8-12 SAE N/A N/A

Stop Poking Your Fingers

One of the most aggravating parts of AN hose assembly is trying to insert the freshly cut end of a stainless braid hose into the AN fitting's socket. More often than not blood is drawn as the hose slips around on the inlet of the socket and the individual stainless wires poke your fingertips. It's not a pleasant feeling; one that we can attest to having endured dozens of times over the years making AN hoses for various project cars. Now you can put the box of Band-Aids away thanks to the invention of Koul Tools. With the Koul Tool, you simply insert the AN fitting's socket into the tool, place the tool into your vice, and push the AN hose into the end of the tool. The tool's funnel like action helps direct the hose's stainless braid into the socket with ease, and best of all, not a drop of blood or a single curse word will ensue! Koul Tools are available for all popular sizes of AN hoses used in automotive projects and the company's latest tool, the EZ-ON hose press, is designed to help assemble push-on style hose without any fuss, too. You can find Koul Tools at Summit Racing, along with AN wrenches and all manner of AN hose and fittings.

Tricks and Tips of AN Hose Assembly

Now that you've gone through our complete guide on assembling AN hoses and fittings, you're probably itching to head out to the garage and try building a hose for yourself. Well, hold on a minute there sparky; we've got a few more tips to make sure everything goes smoothly for you and your hose building adventures.

You get what you pay for with AN hardware. Stick with known products and don't buy farm-quality stuff at the flea market.

Stick to one brand. Not all brands are the same, and while they all transfer fluids well, fitting sizes, fitting-to-hose compatibility, and even colors (one company's black is not the same as another company's black) can differ. Find a company with the fittings you need in the color you want and stick with them for your project.

Keep your fluid flow routing as gentle as possible. A twisting, turning path of 90- and 180-degree fittings is going to cause restriction and generate heat in your fluid transfer. Use as many straight fittings as you can and gentle hose bends.

Use you vice (you do have a vice in your shop right?) with a set of soft jaw vice inserts (pictured here) to protect and secure your fittings during assembly.

AN fittings are reusable, but PTFE hose fittings should be reassembled with a new olive.

AN sealing washers are available to help seal fittings to adapters when quality or brand differences cause minor leaks.

AN hose with stainless braid can cause surface damage if not secured, including cutting through wiring and hoses. Always use clamps and high-strength tie wraps to secure your hose runs or cover the braid with anti-chafe covering.

When choosing the proper AN hose you need to determine pressure, temperature range, and fluid compatibility— carbureted line pressure is much different than EFI line pressure, for example. If in doubt, ask the manufacturer.

Hose assembly routing/design should always take into consideration that the hose must not be kinked, twisted, or have an excessive bend radius once installed.

Lubricate all end fitting and adapter threads before installation; do not thread dry aluminum parts together.

Attach one end of the hose and just snug the end fitting, this allows the opposite end to be threaded and the hose to rotate for the best routing and to prevent twisting. Tighten both ends only after the hose is properly oriented.

Flush all hose assemblies after installing end fittings and blow out with compressed air. If the line is for a high-pressure application, we suggest having the assembled hose pressure tested at your nearest hose crimping/hydraulic outlet.