HOSE END STYLES
Pictured here is an Earl's "Auto-Fit" straight hose end. The Auto-Fit design does not allow swiveling after assembly, placing the hose end in a fixed position. The Auto-Fit hose ends are offered in all the same sizes and shapes as the swivel line, but cost a bit less. When you're performing hose assembly using this style, and if you're using an angle hose end at each end of the hose, you'll simply need to pay attention to hose end clock position to align to the fittings.
-AN hose ends are also available for hose slip-on applications. The female thread accepts dash size fittings, but the hose end features a barbed tube. This design offers easy assembly, but is designed to be used only with specific hose intended for this type of application, and will not work with stainless braided hose. This is a popular and economical option for OE replacement hose assemblies. Available in all popular sizes and shapes.
NOTE: Depending on the size of the AN hose end, assemblies with pipe thread connections are available in a full range of NPT sizes, from 1/8" NPT all the way up to 1/2" NPT (with 3/4" NPT also available from some makers). Generally, hose ends that feature female dash-size connections are designed to accept the same hose dash size at each end (for instance, a hose end may be labeled "-6 female to -6 hose," which means that a -6 hose will connect to the tube/sleeve end, and the female threaded connection will accept a male-thread -6 fitting). However, some makers offer sizing differentials. For example, a -6 female to a -8 hose hose-end might be available to suit a specialty need. However, the most common approach for hose ends is a design that accommodates the same dash size at each end.
We're all accustomed to seeing braided stainless-steel hose with blue and red hose ends on custom cars and race cars. However, great strides have been made by the various hose makers, resulting in a wide array of choices with various benefits. There's certainly nothing wrong with stainless braided hose. It works great and looks great. The only downside of stainless braided hose is its weight and its abrasive outer surface. Although the durable stainless braid does a wonderful job in protecting the hose itself, this surface can scratch, or even file-through an adjacent surface if the hose rubs against anything. Where weight savings are needed, and/or abrasion damage needs to be avoided, the industry now offers a selection of optional hose designs that are lighter and that won't abrade nearby surfaces, but still provide the strong reinforcement and protection for the hose itself. One type isn't better than another...it's simply a matter of selecting the type that best suits a particular application or preference.
A dry sump pan-to-pump scavenge plumbing. Beauty plus brawn. Form and function, etc. You get the drift. It works at a pro level and looks cool to boot. As an alternative to stainless braided hose, lighter-weight high-performance hose is offered with Kevlar outer woven braid or nylon braided sheathing, and special elastomeric hose that features no outer braided cover. Synthetic rubber hose featuring interior braided fabric sheath (for strength) is available with maximum pressure ratings in the 250 psi range and can be assembled using hose nipples and beaded tubing. Hoses with a tough, abrasion-resistant outer nylon sheathing bonded to a textile inner braid and synthetic rubber liner can be assembled using traditional AN hose ends or crimp hose ends, with maximum pressure ratings in the 1,400 psi range. Ultra-light Kevlar-outer-sheathed hoses are available that weigh about 50-60% lighter than stainless-steel braided hoses, with maximum pressure ratings in the 1,100-1,200 psi range, but may require only the use of dedicated crimp hose ends. A wide range of choices are available today, not only in terms of weight, flexibility and materials, but in colors as well.
-AN THREAD SIZE
The thread size of the AN hose end and its mating fitting are as follows:
Note: UNJ threads simply refer to the thread root shape. UNJ threads offer stronger threads that are less prone to stress fatigue. Without going into a bunch of engineering lingo, UNJ thread features a shallower thread root, with a more gentle curve of the thread root. This reduces stress concentration. UNJ really stands for Unified Controlled Root Radius thread (so why isn't it called UCRR? Who knows?).
Metric Thread Sizes AN -4 to 8mm x 1.5 AN -4 to 10mm x 1.25 AN -4 to 10mm x 1.5 AN -4 to 12mm x 1.5 AN -4 to 14mm x 1.5 AN -6 to 10mm x 1.25 AN -6 to 10mm x 1.5 AN -6 to 12mm x 1.5 AN -6 to 14mm x 1.5 AN -6 to 16mm x 1.5 AN -8 to 12mm x 1.5 AN -8 to 14mm x 1.5 AN -8 to 16mm x 1.5 AN -8 to 18mm x 1.5 AN -10 to 14mm x 1.5 AN -10 to 16mm x 1.5 AN -10 to 18mm x 1.5 AN -10 to 20mm x 1.5 AN -12 to 14mm x 1.5 AN -12 to 16mm x 1.5 AN -12 to 18mm x 1.5 AN -12 to 20mm x 1.5 AN -12 to 30mm x 1.5 AN -16 to 16mm x 1.5 AN -16 to 18mm x 1.5 AN -16 to 20mm x 1.5 AN -16 to 30mm x 1.5
Aeroquip's Pro Crimp 1380 crimping machine allows easy and fast assembly of AN crimp-type hose ends. Photo courtesy Aeroquip
The fitting (also called adapter) allows the connection of the hose end to the component. In some cases, the fitting will be provided as part of the component (for example, an engine oil cooler might already feature welded-on -10 fittings, so a -10 hose end will thread directly onto the cooler). In other cases, you'll need a separate fitting to finish the connection. Fittings are available with AN threads (and 37-degree flare seat) on one end, and an appropriate thread on the opposite end to fit the component. For example, let's say that you need to plumb a -10 hose assembly to your water pump-to-heater routing. The water pump may feature a 1/2" NPT female threaded hole. In order to complete the connection, you'll need an AN fitting that features a 1/2" male NPT at one end and a -10 male at the opposite end to attach to your hose end. Fittings are available in a wide variety of both thread size combinations to accommodate any reasonably practical connection between various AN hose ends and NPT threads. Fittings are also available in straight thread (as opposed to tapered pipe thread), for locations that feature straight-thread holes. If the AN fitting features straight thread for the component connection, a sealing O-ring will likely be required. Fittings, like hose ends, are also available in various shapes, including straight, 45-degree and 90-degree, to further accommodate plumbing routing and clearance issues. With the combination of hose flex and hose end and fitting shapes, it is possible to achieve extremely neat and tidy plumbing routing that would please even the most demanding appearance-conscious builder. Metric adapters are also available, to accommodate all domestic and import OE vehicle applications for the use of AN 37-degree plumbing connections. The AN threads are the same as always, but the opposite end, instead of featuring NPT or AN straight thread, features metric thread size instead. AN adapters for metric applications are available in all common AN to metric sizes, including:
This example shows an AN adapter with a male AN (37 degree seat) at the right side as shown here, where the hose end will attach; and a straight thread male at the opposite end. Notice the sealing O-ring at the straight thread side. No thread sealant is required for straight threads. If a cone seat is featured, the mating of the 37-degree seats will achieve the seal. If the AN straight threads feature no seating cone, an O-ring is required for sealing.
This fitting features straight threads and a sealing O-ring, which will mate to an aluminum fuel log for a fuel-injected engine. Notice that the fuel log threaded opening features a recess to accommodate the O-ring. Note: as far as hose end and fitting materials are concerned, both steel and aluminum are available. For purposes of weight saving and appearance, most people favor aluminum (as you already know, hose hardware makers commonly offer aluminum AN hose ends and fittings in blue and red anodized colors). However, for brake system connections, steel hose ends and fittings are often preferred to avoid the however-unlikely potential for fatigue cracks. ALUMINUM NPT TO AN ADAPTERS Fitting adapters that allow connection between pipe thread locations and AN hose ends. Photos courtesy Earl's
Female NPT to male NPT reducer. This allows the use of a smaller NPT male fitting at a larger female NPT hole. For example, if the female NPT hole in an intake manifold featured 1/2" NPT threads at a water jacket port, but you want to connect a 3/8" NPT fitting, this pipe bushing reducer would allow that change.
90-degree female NPT to female NPT elbow. Same size NPT at each end shown here.