6AN to 4AN(1/4)NPT Union Adapter 90

The 6AN to 4AN (1/4) NPT union adapter 90 by Redhorse Performance is an essential hydraulic line fitting for custom fuel, coolant, and brake system plumbing on modified vehicles. This 90-degree adapter bridges between -6 AN hose and 1/4-inch NPT port threads, making it indispensable for engine bay routing where space constraints demand compact directional changes. Whether you're building a fuel system for a turbocharged engine, installing remote oil coolers, or fabricating custom cooling loops, this adapter provides the reliable connection point that separates amateur work from professional-grade installations.

Redhorse Performance designs this union adapter with precision aluminum construction and teflon-lined threads to prevent ANO corrosion and ensure leak-free seals under boost pressure and thermal cycling. The 90-degree elbow geometry allows you to route -6 AN hose (typically 3/8-inch ID) to standard NPT-threaded components—oil coolers, thermostats, fuel pressure regulators, and intercooler tanks—without resorting to undersized adapters that create pressure drops and heat retention. The compact 2.75-inch overall length and lightweight 0.06-pound design minimize fitment complications in tight engine compartments while maintaining full flow capacity for high-demand cooling and fuel delivery systems.

Serious fabricators and performance builders rely on this adapter for forced-induction setups, custom water cooling loops, and standalone fuel systems where OEM components no longer fit the modified engine layout. Installation requires standard 9/16-inch wrenches and standard thread sealant on the NPT side; the -6 AN side accepts JIC reusable or disposable hose fittings. Compatibility spans domestic and import platforms—LS swaps, turbo 4-cylinders, and complete restomod builds—making it a versatile stock item for any serious shop or home garage tackling modern performance plumbing.