Choosing the correct AN fitting sizes is essential for ensuring the safety, efficiency, and reliability of your automotive fuel system. AN fittings are used to connect hoses and lines that carry fuel, oil, and other fluids under pressure. Using the right size prevents leaks, maintains proper pressure, and avoids costly damage.

Understanding AN Fitting Sizes

AN fittings are standardized by the Aerospace National (AN) sizing system, which indicates the size of the fitting through a number that corresponds to the inner diameter of the hose or tube in sixteenths of an inch. For example, an AN-6 fitting has an inner diameter of 3/8 inch.

Common AN Fitting Sizes for Automotive Fuel Systems

  • AN-4: Suitable for low-pressure fuel lines, typically used in small or auxiliary systems.
  • AN-6: The most common size for high-performance fuel lines, offering a good balance of flow capacity and flexibility.
  • AN-8: Used for high-volume fuel delivery, such as in fuel pumps or large-diameter lines.

Choosing the Right Size for Your Vehicle

To select the correct AN fitting size, consider the following factors:

  • Fuel flow requirements: High-performance or racing vehicles may require larger fittings (AN-6 or AN-8).
  • Existing system compatibility: Match the fitting size to your current lines and fittings to ensure proper connection.
  • Pressure levels: Higher pressures demand secure fittings that can handle the load without leaks.

Tips for Installing AN Fittings

Proper installation is key to a safe and efficient fuel system. Here are some tips:

  • Use the correct tools, such as a flare or AN wrench, to tighten fittings without over-tightening.
  • Ensure all threads are clean and free of debris before installation.
  • Apply a compatible thread sealant or flare to prevent leaks, if recommended.

Conclusion

Choosing the right AN fitting size is crucial for maintaining a safe and efficient automotive fuel system. Understanding the sizing system and considering your vehicle's specific needs will help you make the best choice. Proper installation further ensures long-lasting performance and safety.