4AN to 6AN 3/8NPT Straight Male to Male

The 4AN to 6AN 3/8NPT Straight Male to Male fitting from REDHORSE PERFORMANCE is an essential adapter for custom fuel, coolant, and brake line plumbing in modern engine builds and performance modifications. This straight male-to-male connector bridges two different AN hose sizes—a critical requirement when routing lines through tight engine bays or integrating aftermarket fuel systems, turbo coolers, and custom cooling loops. Whether you're upgrading to a larger fuel delivery system, installing a secondary fuel pump, or reconfiguring your cooling circuit, this fitting provides a leak-free connection point that maintains system integrity under pressure.

Constructed with precision machining, the 4AN to 6AN adapter features 37-degree flare ends on both the 4AN and 6AN sides, ensuring industry-standard JIC fitment that eliminates micro-motion and vibration-induced leaks common in undersized adapters. The 3/8NPT (National Pipe Thread) male port allows integration with NPT-threaded components like pressure sensors, coolant tanks, or transmission coolers without requiring secondary adapters. REDHORSE Performance fittings are engineered from aerospace-grade aluminum or steel, delivering reliable performance across fuel, oil, and coolant applications up to typical system operating pressures, making this adapter suitable for naturally aspirated and turbocharged engine platforms alike.

This fitting is ideal for fabricators, engine builders, and performance enthusiasts transitioning between AN hose diameters in fuel rails, intercooler lines, and custom plumbing scenarios where off-the-shelf solutions don't exist. Installation requires standard AN wrench sizes and compatible hose clamps or clocking collars; always use thread sealant tape or pipe dope on the NPT port to prevent weeping. Verify flow direction and component pressure ratings before assembly, and test under load to confirm zero seepage, especially in high-vibration or underhood environments where thermal cycling accelerates joint degradation.