Introduction
If you've ever looked under the hood of a built race car, you've probably noticed braided lines running through the engine bay. These are AN fittings and hoses, a standardized system initially developed by the U.S. military (Army-Navy, or AN) that has become a staple in motorsports. Whether you're a beginner wondering where to start or an experienced builder looking for some expert tips, this guide will walk you through everything you need to know about AN fittings, hose types, and assembly techniques.
In this in-depth tutorial, I'll cover the basics of AN sizing, different types of fittings, and how to assemble both rubber and PTFE hoses correctly. By the end, you'll have the knowledge and confidence to build reliable, leak-free lines for your car’s fuel, coolant, or oil system. Let's dive in!
What Are AN Fittings and Hoses?
AN fittings and hoses are widely used in motorsports due to their reliability and reusability. These fittings ensure leak-free connections without needing additional sealing tape or adhesives. Their widespread adoption has led to a vast range of options, allowing builders to plumb virtually any part of a vehicle with AN lines.
AN Sizing Explained
AN fittings come in sizes ranging from -2 to -32, with the number representing sixteenths of an inch in outside diameter. Here’s a quick reference guide:
- -4 AN: 1/4 inch OD (Common for brake lines)
- -6 AN: 3/8 inch OD (Common for fuel lines)
- -8 AN: 1/2 inch OD (Often used for fuel or oil lines)
- -10 AN: 5/8 inch OD (Ideal for oil cooling applications)
- -16 AN: 1 inch OD (Common for radiator hoses)
- -20 AN: 1-1/4 inch OD (Used for high-flow coolant systems)
This system ensures compatibility and makes it easy to select the right size for each application.
Common AN Fitting Angles and Connection Types
AN fittings are available in various angles to help route hoses efficiently:
- Straight
- 30-degree
- 45-degree
- 60-degree
- 90-degree
- 120-degree
- 150-degree
- 180-degree
Connection Types
- Female AN Hose Ends
- The most common type, designed to thread onto male AN fittings.
- Seals via a 37-degree flare without the need for additional sealants.
- ORB (O-Ring Bung) Fittings
- Common in water pumps and fuel rails.
- Uses an O-ring to create a reliable seal, reducing the chance of leaks.
- NPT (National Pipe Thread) Adapters
- Often mistaken for ORB but has tapered threads that require sealing tape.
- Banjo Fittings & Hard Line Adapters
- Used in tight spaces where a direct hose connection isn’t feasible.
Each of these has its place depending on the system being plumbed.
How to Cut AN Braided Hose Properly
There are several ways to cut AN hose, but not all of them are ideal. Here are your options:
- Angle Grinder/Hacksaw (Not Recommended)
- Produces a clean cut but leaves behind rubber and metal debris inside the hose.
- Hard to fully clean, increasing contamination risks.
- AN Hose Shears (Recommended)
- Provides a clean cut with no debris inside.
- Prevents fraying and makes assembly easier.
Pro Tip:
Wrap the hose with non-adhesive tape before cutting to prevent the braided stainless steel from fraying.
Assembling a Rubber AN Hose
- Insert the Hose End Socket
- Push the hose into the socket until it seats fully.
- Clamp the Socket in a Soft-Jaw Vise
- Prevents damaging the anodized finish.
- Lubricate the Hose End Threads
- Use silicone spray or a few drops of motor oil for easier threading.
- Thread the Fitting Together
- Use an adjustable AN wrench to tighten it down.
- Leave a 1/16-inch gap between the two halves to prevent overtightening.
Final Thoughts & Call-to-Action
Plumbing your car with AN fittings can seem overwhelming at first, but once you understand the sizing, fitting types, and proper assembly techniques, it becomes a rewarding process. Investing in the right tools—like AN wrenches, soft-jaw vise clamps, and hose shears—will make your life significantly easier.
Have you used AN fittings before? If you have any questions or need further clarification, drop a comment below. And if this guide was helpful, consider sharing it.