What to Know Before Installing AN Fittings on Your Fuel Line

If you're upgrading your vehicle’s fuel system, you’ve likely come across AN fittings. These fittings are known for their leak-proof design and solid performance. 

But before you jump in and start installing them, there are a few things you should know. This guide will help you make the right choices and avoid common mistakes.

What are AN Fittings?

AN stands for Army-Navy. These fittings were first developed for military use. Today, they’re widely used in motorsports and street builds. AN fittings are known for their strong, reusable, and tight-sealing qualities. They’re ideal for fuel, oil, and coolant lines.

Each fitting has a 37° flare. This creates a strong seal when connected. They come in various sizes and angles. Most performance setups use 4AN, 6AN, 8AN, or 10AN.

Why Use AN Fittings?

AN fittings offer a solid upgrade over rubber hoses and hose clamps. They reduce leaks. They make lines easy to disconnect and re-route. They can also handle more pressure and heat.

If you're building a turbocharged car or a high-horsepower setup, these fittings are a must. They also give your engine bay a clean, professional look.

Know Your AN Sizes

AN fittings are labelled by dash sizes. Each dash size equals 1/16 inch. For example:

• 4AN = ¼ inch

• 6AN = ⅜ inch

• 8AN = ½ inch

• 10AN = ⅝ inch

Make sure to match your fitting size with your hose and fuel rail ports. Don’t guess. Always measure the outer diameter of the hose or use a sizing chart.

Material Matters

Not all fittings are made the same. Look for 6061 billet aluminium fittings. These offer strength without extra weight. Stainless steel fittings are also strong, but are heavier and may corrode less over time.

Choose anodized fittings for better durability. Anodizing adds a hard outer layer that resists wear and corrosion.

Straight vs Angled Fittings

AN fittings come in straight, 45°, 90°, and 180° angles. The right angle helps your fuel lines route cleanly. You don’t want hoses to kink or twist. That can restrict flow or cause stress on the fitting.

Use straight fittings where space is open. Use 45° or 90° fittings near bends or tight spots. Always mock up your lines first to find the best angle.

Make Sure You Use the Right Hose

AN fittings don’t work with every hose. You need PTFE or braided stainless steel hoses. These can handle the pressure and won’t collapse or leak. Don’t use standard rubber hoses. They won’t seal properly and may slip off.

Cut the hose clean and square. Use a hose cutter or fine-tooth saw. Frayed ends will make it hard to install the fitting correctly.

How to Install AN Fittings

Installing AN fittings takes patience. Here are the steps:

1. Cut the hose clean.
2. Slide the collar onto the hose.
3. Push the hose into the fitting until it bottoms out.
4. Lubricate the threads lightly with assembly lube.
5. Thread the collar and fit it together.
6. Use two wrenches to tighten them. One for the fitting, one for the collar.
7. Do not over-tighten. You want a snug seal, not crushed threads.

Testing the Fit

Once everything is tight, test the fuel line before installing it in your car. Pressurize the line with air or fluid. Check for leaks. If you see bubbles or drips, redo the fitting. Leaks in a fuel system can be dangerous.

Check again once the lines are in place and the engine is running. A second check can catch issues before they become serious.

Common Mistakes to Avoid

• Wrong hose type – Always use braided or PTFE hoses.

• Loose fittings – Tighten correctly to avoid leaks.

• Poor cuts – Use proper tools to cut the hose clean.

• Forcing angles – Use angled fittings where needed to prevent stress.

• Mixing sizes – Match all ends properly to avoid misfit and leaks.

What Makes Good AN Fittings?

High-quality AN fittings should be reusable, lightweight, and corrosion-resistant. Look for fittings with smooth threads and a tight tolerance. A good fitting will thread on cleanly without force.

You can find top-tier options at NGR Performance. These fittings are made from high-grade materials, anodized for extra protection, and come in multiple angles and sizes.

If you're focused on clean builds and power handling, the performance of AN fittings makes all the difference. They’re built for more than looks—they’re engineered to keep your lines secure under pressure.

When to Replace AN Fittings

Though many AN fittings are reusable, inspect them during every install. If you see cracks, worn threads, or damage to the flare, replace the fitting. Also, check the hose ends. If the hose is fraying or feels loose, cut and reinstall it.

For long-term reliability, don’t reuse damaged parts. Leaking fuel or oil can cause fires or performance issues.

Essential Tips for a Clean Install

• Plan your hose routing before cutting.

• Use clamps or separators to hold lines in place.

• Keep hoses away from heat sources like exhaust headers.

• Double-check the torque on every fitting.

• Label your lines if needed.

Taking your time now prevents costly mistakes later.

Trust Your Setup with NGR Performance

Installing AN fittings on your fuel system is one of the smartest upgrades you can make. It improves reliability, reduces leaks, and helps your engine breathe better under pressure.

Whether you're building a daily driver or a track car, a clean, secure fuel system matters. Use the right tools, take your time, and avoid shortcuts. And when you're ready to upgrade, choose fittings designed to last.

You'll find high-quality, race-proven components built for real power at NGR Performance. Our range of AN fittings offers the performance, fit, and finish your build deserves.