Fuel System Plumbing - We Build New Fuel Lines With Earl's Braided Hose

Plumbing automotive fluid systems with high-pressure hose and fittings is a practice that dates back to the post-war era, when GIs returning home began applying the technology they'd observed on military aircraft to their hot rods. Today, the most common use of mil-spec plumbing is stainless braided flex lines connected with AN-style fittings. This system was developed for the military as a means of providing flexible fluid couplings that could be serviced in the field without the need for hydraulic machinery to create crimped hose ends while still coping with high operating pressure. Instead, a heavy-duty rubber hose is sheathed with a stainless steel braid to add burst resistance, raising the operating pressures to over 1,000 psi in many cases. To join the sections of hose, AN fittings were developed, allowing the user to insert a hose end into a fitting, which is then tightened with common hand wrenches to create a high-pressure coupling.

This is the sort of half-assed hosiery often found on modified street machines. A conversion to an aftermarket-style dual-feed Holley done with parts-store rubber hose, cheap plastic T-fittings, and lots of hose clamps. It functions but doesn't look very professional and is likely prone to leaks. On a high-performance engine, this would be totally unacceptable and wouldn't pass a basic NHRA tech screening even for a 14-second car. Improving upon this will not be difficult.

This is the sort of half-assed hosiery often found on modified street machines. A conversi

The stainless braided line appeals to rodders and racers alike for both its severe-duty capabilities and its appearance, but recently, the Earl's division of Holley has introduced an alternative: Pro-Lite 350 hose. The Pro-Lite hose is fabric-braided in nylon, primarily as a means of reducing the weight of the line for racing applications. Despite this, Pro-Lite maintains a 350-psi operating rating and the same temperature range as stainless (-40 degrees F to 300 degrees F). One of the fringe benefits is its ease of service, as Pro-Lite hose can be cut and assembled with less hassle than traditional stainless. For some, the appeal is purely cosmetic, as Pro-Lite's black sheath, which can be matched with black or silver fittings, can be used to create a more industrial look for engine-bay plumbing.

We had a carburetor to plumb, so we opted to try Pro-Lite 350 along with Earl's fittings to tie our Holley fuel pump to the carb. We've utilized some traditional red-and-blue fittings and a bit of stainless hose for this job, but by the time this hits the newsstand, Earl's should have expanded its line of Ano-Tuff hard anodized black fittings, as well as its offerings for clear-finish Auto-Fit fittings, allowing users to plumb without color if so desired. The system is easy to use and not that pricey, so maybe it's time to ditch the rubber hose and worm clamps.

A common sight on both race cars and street machines since the '70s is stainless braided hose coupled with aluminum AN fittings. These products were actually developed for military aircraft and later adopted to performance automotive applications to provide positive sealing of high-pressure fluid systems. The added bonus is looking trick.
A common sight on both race cars and street machines since the '70s is stainless braided h
A recent alternative to stainless braided line is Pro-Lite 350 fabric braided hose, offered by the Earl's division of Holley. Pro-Lite 350 is rated at 350-psi maximum operating pressure, which is less than traditional stainless hose, but more than enough for most automotive applications, and Pro-Lite offers some advantages over traditional stainless line. Racers are most interested in the weight savings it can provide-we're told a typical Hooters Cup car can shed around 30 pounds by switching the fuel, oil, and cooling lines to Pro-Lite. Pro-Lite can also withstand the same temperatures as stainless line, being rated from -40 degrees F to 300 degrees F.
A recent alternative to stainless braided line is Pro-Lite 350 fabric braided hose, offere
For those interested in matching the black sheath of the Pro-Lite hose, Earl's carries both black and silver fittings. The black pieces are part of the Ano-Tuff line of Swivel-Seal fittings and are actually hard-anodized, offering extra protection against corrosion (designed with alcohol racers in mind) and chipping. The silver fittings are actually bare aluminum with a clear coating and are found in the Auto-Fit line.
For those interested in matching the black sheath of the Pro-Lite hose, Earl's carries bot

To better illustrate the process of plumbing a typical Holley carb, we'll use this stand-mounted engine. Up top is a Holley Street Avenger 660 carb with the standard dual-feed arrangement. To feed it, we've installed a Holley mechanical fuel pump. Now we just have to sort out a means of joining the two.
To better illustrate the process of plumbing a typical Holley carb, we'll use this stand-m
There are many ways to connect the bowls of a dual-feed carb to the main fuel line, but the simplest is probably a fuel "log" or manifold. By the time you read this, Earl's will be offering a fuel manifold using the Pro-Lite 350 braided line with the black hard-anodized fittings. For our story, we used the standard manifold with stainless braided line and red/blue fittings, since the new black stuff was not quite ready yet. Installation is simply a matter of threading the fittings into the carb's bowl inlets. Earl's recommends using aluminum seal washers rather than the steel washers typically found on Holley-style bowl nuts.
There are many ways to connect the bowls of a dual-feed carb to the main fuel line, but th
At the fuel pump, a 90-degree fitting is installed to convert from the pump's NPT pipe-threads to a male AN while also aiming up at the carb. The pipe threads require some form of sealer, particularly since the fitting has to be indexed to face in the desired direction rather than bottomed out. We wrapped the pipe threads with Teflon tape, which is an acceptable practice, though many racers prefer liquid Teflon sealant (Permatex offers such a product), fearing that errant bits of the tape could wind up in the carb's needle-and-seat. To avoid this, we wrap the tape tightly a few threads back from the fitting's end. Do not use tape or sealer on the AN fittings.
At the fuel pump, a 90-degree fitting is installed to convert from the pump's NPT pipe-thr

This is one of the simpler plumbing jobs you'll encounter, particularly since it only requires a single line to bridge the distance. We started by measuring the span with a tape measure, but many experienced engine plumbers will use string or a bent wire to represent the distance, taking into account the required bends.
This is one of the simpler plumbing jobs you'll encounter, particularly since it only requ
Another benefit of Pro-Lite hose is that it can be cut much more easily than stainless braided line. Earl's still recommends wrapping the hose tightly with duct tape at the point to be cut and then using heavy clippers to make the slice. We actually found that an even stroke with a fresh razor blade or craft knife created a precise cut with little or no fraying of the fabric, even without the tape.
Another benefit of Pro-Lite hose is that it can be cut much more easily than stainless bra
Tom Neely of Earl's Store #1 in Lawndale, California, often uses a large, sharp concrete chisel and a block of aluminum for a crisp, clean cut-a practice he developed for servicing stainless braided line at the track. The ultimate objective is to have a clean cut that is square with the hose itself.
Tom Neely of Earl's Store #1 in Lawndale, California, often uses a large, sharp concrete c

Before the fittings can be assembled on the hose, they should be disassembled for lubrication. We used Earl's own liquid lube intended just for this purpose, but Earl's says engine-assembly lube or engine oil are both sufficient. Without the lube, the aluminum fittings can easily gall, possibly ruining them.
Before the fittings can be assembled on the hose, they should be disassembled for lubricat
The first step in fastening the fitting to the hose is to slip the hose through the fitting's socket while it is removed completely from the rest of the fitting. With stainless braided line, this often requires that the socket be secured in a vise, but the fabric-braided line can be manipulated much more easily. Slip the hose up until it butts against the bottom of the threads inside, then pull it back until there is a 1/16- to 1/8-inch gap between the hose end and the threads. The hose should then be marked at the base of the socket for reference.
The first step in fastening the fitting to the hose is to slip the hose through the fittin
Next, the fitting should be clamped in a vise. Obviously, the jaws of a standard vise will gouge the fitting if no preventative measures are taken. We wrapped our fitting in heavy cloth tape (duct tape will do) before tightening down on it. The fitting should be positioned so the threads protrude from the jaws, allowing you to push the hose against the fitting's nipple. Grip the hose (not the fitting) and push while twisting to engage the threads of the socket with those of the fitting.
Next, the fitting should be clamped in a vise. Obviously, the jaws of a standard vise will

Once the threads are started, loosen the vice and reposition the hose assembly so that the socket is gripped in the jaws (again, wrapped in tape) and the fitting is accessible. Then the fitting must be tightened into the socket. Using standard wrenches on the fittings will likely mar their finish, so a set of special aluminum AN wrenches is a good investment. Watch the reference mark made earlier to make sure the hose isn't being pushed out, rather than clamped. A slight bit of push is expected, though.
Once the threads are started, loosen the vice and reposition the hose assembly so that the
After our flex hose is assembled with fittings, all that remains is to thread it onto the fuel pump and the carb's inlet and snug it up, again using aluminum AN wrenches.
After our flex hose is assembled with fittings, all that remains is to thread it onto the
Our carb has internal filters, but for applications requiring an inline filter, Earl's offers an anodized aluminum unit with a removable sintered bronze element and male AN fittings on each end, in either -6 or -8.
Our carb has internal filters, but for applications requiring an inline filter, Earl's off