How to Plumb Your Vehicle
Slide Show
Whether it’s in your bathroom or on your race car, plumbing can be an exercise in frustration—especially when you finish the job, turn on the faucet or switch on the pump, and discover you have more leaks than flow.
While we can’t help you much with bathrooms, we can show you how to assemble leak-free hose and fittings for your car, with a little help from the plumbing guys at Earl’s.
For our example, we’ll be plumbing a Holley “blue” electric fuel pump using Earl’s Swivel-Seal AN fittings, Perform-O-Flex braided hose, and Summit Racing 3/8 inch aluminum hard line. The basic assembly procedures used here apply to most automotive plumbing.
We also have a list of tools that will help you do a first-class plumbing job, plus some general tricks and tips to make you the AN Plumbing Master of the Universe. Well, at least of your neighborhood.
Hose and Fitting Tips
1. You’ve probably heard this one before, but AN stands for Army-Navy. Established many years ago by the U.S. military as a common measurement for hose and fittings, it designates the outside diameter (o.d.) of the rigid metal tube that is compatible with each size fitting. These dash sizes are expressed as the numerator of the fraction, with the denominator always being 16. For example, a –04 port is 4/16, or 1/4 inch.
Here a list of common AN to fractional equivalents:
-02 AN = 1/8 inch
-03 AN = 3/16 inch
-04 AN = 1/4 inch
-05 AN = 5/16 inch
-06 AN = 3/8 inch
-08 AN = 1/2 inch
-10 AN = 5/8 inch
-12 AN = 3/4 inch
-14 AN = 7/8 inch
-16 AN = 1 inch
-20 AN = 1 1/4 inches
-24 AN = 1 1/2 inches
-32 AN = 2 inches
2. Over-tightening is one of the most common ways to destroy an aluminum fitting. It can distort a fitting’s seat or cone, making it prone to leaks. Dirt and debris on the sealing surface can also cause a fitting to leak. Make sure to clean out a hose/fitting assembly with solvent after putting it together to remove shavings or other debris.
3. Believe it or not, vacuum hoses take more abuse than any other type. It is important to match the hose to the vacuum rating of your application. If a hose is installed beyond the minimum bend radius, or has been kinked or damaged, its vacuum rating will be reduced. For severe vacuum applications, such as dry sump oiling systems, an internal support coil may be needed. Earl’s has these coils in various inside diameters.
4. Abrasion is one of the leading causes of hose failure, hence the popularity of hose like Earl’s Perform-O-Flex hose with tough stainless steel braided covers. For racers looking for less weight, Earl’s Pro-Lite 350 hose has a braided nylon cover and weighs far less than steel braid-covered hose. No matter which type of hose you use, make sure to route it to avoid sources of heat and contact with other components. Use support clamps to keep the hose from flopping around and rubbing against frame rails, headers, and other stuff.
5. When cutting braided hose, clean up any burrs and ragged edges on the end of the hose. This helps to ensure a secure, leak-free seal between the hose and the fitting. Wrap the end with electrical tape before cutting to help minimize burrs and ragged edges.
