The Day the Sportsmen Fought Back

Greg Anderson Interview

Why Is Super Chevy so Profitable?

The NASCAR & Drag Racing Connection

Bobby Warren

Comp Eliminator: Where the Variety Is

Jeff Arend’s Diamond in the Rough

Remembering the Good Old Days

The Making of the Hot Rod Reunion

Tony Stephenson – Comp Hitter

Plumbing your Race Car -Part 2

The Rattler Strikes

The Art of Carburetor Maintenance

“Project Muscle” Wrap-up

Darrell Russell Remembered

IHRA Milan

IHRA Milan – Photo Gallery

NHRA Denver

NHRA Denver – Photo Gallery

NSCA Quaker City

NSCA Quaker City – Photo Gallery

NHRA Seattle

NHRA Seattle – Photo Gallery

IHRA Toronto

IHRA Toronto – Photo Gallery

NHRA Sonoma

NHRA Sonoma Photo Gallery

IHRA Martin

IHRA Martin – Photo Gallery

NHRA Brainerd

Holley National Hot Rod Reunion Recap

Holley National Hot Rod Reunion – Photo Gallery

The Francis Butler Showdown

The Francis Butler Showdown – Photo Highlights

IHRA – Edmonton

IHRA Edmonton – Photo Gallery

NHRA St. Louis

NHRA St. Louis Photo Gallery

NHRA AMS St. Louis

NHRA AMS St. Louis Photo Gallery

Fun Ford Weekend

Ten-Five Racers Association – Reynolds, Ga.

Ten-Five Racers Association – Photo Gallery

ANDRA – Winternationals – Photo Gallery

Goodguys – Pomona

Goodguys – Pomona Photo Gallery

Last issue, we took the first look at plumbing a race car. In that article, we looked the varied thread formats used in the automotive plumbing world. We also looked at aircraft (AN) numbers. They're decidedly different. This time around, we'll show you how to mix the two (automotive and AN). Check out the following:

Mixing & Matching...

In order to adapt A-N (Army-Navy) hose ends to a part designed with pipe threads, you'll need an adapter. All fitting companies offer them, and there are countless configurations. Believe it or not, adapter fittings are not created equal. And that's particularly true when it comes to adapter fittings for fuel delivery systems.

A common #8 A-N fitting makes use of a 3/4-16 SAE straight thread. This type of thread allows for very easy assembly and disassembly. It won't leak (due to the internal sealing taper) and it's easy to work with. The outer hex on the #8 A-N fitting is 7/8". In this case (the socket hex) all pieces of the hose end are the same size. But in larger and smaller straight fittings (along with some bent tube fittings), the hex size may vary between the three parts of the fitting.

Fittings are fittings - what's the difference? Take the common AN adapter fittings used on a cathedral-style Holley carburetor bowl as an example. These fittings usually "adapt" a number six or eight A-N hose end to the special Holley 7/8-20 bowl thread. No big deal -- right? Oh yes it is. You see, the majority of standard fittings used in this application are stepped during the machining process. In other words, the internal bore isn't smooth. It has a machined step on the ID (in the fuel fitting application, the step is smaller on the A-N side). Several of the after market fuel delivery companies (John Rademacher's Product Engineering is one) reasoned that if the bore was smooth, there wouldn't be turbulence inside the fitting. And if the bore was consistently larger, then more fuel could be delivered to the bowl. The result would be a much more even (and efficient) delivery of fuel.

During bench (and real world) testing of the fittings, Product Engineering found that the simple removal of the step along with the "smoothing" of the fitting bore resulted in an amazing increase in fuel flow. Just how much of an improvement was found? Depending upon the size of the fitting (#6 or #8), the fuel flow through the fitting increased by 24 to 36%. Those are astounding numbers, but almost as important, the larger inside diameter of the fittings provided a small, but necessary "reservoir" of extra fuel. Now that extra "reservoir" of fuel might not be significant in all applications, but when a fuel delivery system is taxed to the maximum, every little bit helps. The final improvement was the reduction of turbulence introduced into the carburetor bowl by the fitting.

There's more to the decreased turbulence than first meets the eye. Given the success found with the simple carburetor fittings, they looked at the #10 and #12 fittings that are commonly used on dry sump oil pumps and other locations in a car (such as a high volume fuel system). In this application, it was found that a smooth radius on the inlet side of the fitting might help the flow of lubricant going out of the pump. After considerable experimentation and testing, they developed a special radius on the inlet side of the fitting that places the lubricant into a laminar flow condition. Translated, this means that fitting does not create tumbling of the liquid molecules. As a result, the wall friction inside the hose or line that follows the fitting is reduced by a significant margin. This in turn, allows the core to move the fluid (whether that fluid is gasoline, alcohol, oil or whatever) more freely.

This is the tapered pipe thread we talked about earlier. No matter how sophisticated your race car is, you will run into NPT somewhere. And it will eventually have to be adapted to A-N. If, for example, you have a fuel pump with 1/2" NPT female ports, and the fuel line you've decided to use is -10, you'll obviously need some sort of adapter. In this case, you'll need a 1/2" pipe to -10 A-N adapter with two male ends -- one with 1/2" NPT and the other with -10 A-N. The adapter is sealed (on the pipe thread end) with Teflon tape or paste and attached to the fuel pump. With the adapter in place, you can now add the hose and hose end combination.

As expected, this type of fitting also has other uses, and that includes the pickup points of a fuel tank, the outlet of an oil cooler and in smaller applications, the outlet side of a mechanical fuel pump. Fortunately, Product Engineering and other companies offer a complete line of flowed A-N "adapter" fittings that are applicable to myriad fluid transfer locations in your car. Naturally, you can't expect these fittings to be miracle cures for all fluid-movement woes, but if you're looking for an edge, this is a good place to start.

In the text, we mentioned high flow fittings. When you have a close look at the inside diameter of these fittings, you'll find a relatively large bore, but just as important, there is no machined "step" inside the fitting. The entire line of adapter fittings were developed using fluid flow testing and as a result, flow through a simple carb fitting can be anywhere from 24% to 36% greater than in a conventional job.

Another point to consider, and one we discussed with John Rademacher is the type of hose end use on fuel delivery systems. The bottom line when it comes to fittings and adapters is to avoid sharp bends if possible. Why? Simple. Straight fittings constitute the lowest flow restriction. OK. That's great, but what if you need a bend in the system? Then use a bent tube fitting (the type with a metal tube between the hose socket and the A-N threaded end). These fittings have superior flow characteristics when compared to the forged 90° bends. The last resort is a forged 90° fitting. Yes, it makes a nice tight bend, but when in use, the fuel has to make an abrupt turn as well. 90° adapters should also be avoided (if possible) for the same reasons.

This is why the high flow fittings have appeared on the marketplace: Some after market fittings are machined from either end. Because of this, they will often have a visible step on the ID. This can create a good amount of turbulence inside the fitting. Unfortunately, this turbulence is often carried through the fluid transfer hose. A good place to make use of the "re-engineered radius" found on a high flow fitting is the fuel cell (or tank) outlet fitting. As you can see, the radius is very generous and as a result, fluid flow out of the fuel cell or fuel tank is improved considerably. Essentially, the friction inside the hose is reduced -- this is done by moving the fluid transfer into the hose "core", not near the wall.