AN thread has long been considered the go-to standard in high performance fluid transfer tube fittings. A deep dive into Holley’s vast technical library uncovered an interesting tidbit that many old car buffs might not even be aware of: AN is short for “Army-Navy” and the thread size was created decades ago for the high-precision aerospace industry.

It stands to reason that if it’s good enough for military equipment, then it’s good enough for muscle car applications as well. Six Pack Mopars are now able to take full advantage with Earl’s Performance Plumbing’s recently-released -6 AN fuel line kits. Pre-assembled braided hoses are available in stainless steel (P/N PK0016ERL) and black polyester (P/N PK0015ERL) material.

If not done correctly, the factory flared connection points can be leak prone and the rigid tube doesn’t provide any flexibility at all. Earl’s -6 AN hose fixes both of those problems and, as an added bonus, are a little bit bigger than the factory 5/16” hard line. The AN sizing concept is relatively simple. Sizes are designated by “dash” numbers that correspond to the outer diameter of a comparable metal tube.

Basically, you take the “dash” number divided by sixteen and come up with a nominal tube or hose size. For example, -6 AN hose translates to a 3/8” (6/16”) diameter. The seal within the fittings is facilitated by a metal-to-metal contact of a 37-degree flare that should be trouble-free for plenty of miles.