Bulkhead Nut #4

The FRAGOLA Bulkhead Nut #4 is a precision aluminum bulkhead fitting designed for custom fuel system builds, hydraulic brake lines, and cooler line installations on performance vehicles. Whether you're assembling a fuel cell in a race car, installing a remote oil cooler on your daily driver, or upgrading to -4 AN braided hose runs, this bulkhead nut serves as the sealed connection point that keeps your system leak-free under pressure.

Engineered from lightweight aluminum alloy, the #4 bulkhead nut features a compact footprint of 1.05 inches in length that fits tight engine bays and confined fabrication spaces without sacrificing strength. The nut's knurled or smooth outer diameter allows secure hand-tightening and wrench engagement, while the internal thread geometry ensures a reliable seal when paired with matching bulkhead fittings or manifold blocks. This construction resists corrosion better than steel alternatives, extending the service life of your custom plumbing.

This bulkhead nut is essential for engine swap projects, fuel system upgrades, and custom cooling loops where OEM connectors won't fit your layout. Mechanics and fabricators rely on FRAGOLA fittings because they meet rigorous SAE standards and maintain integrity in high-vibration environments. At a verified weight of 0.02 lbs, it adds negligible weight to any system—critical for weight-conscious builds—yet withstands sustained pressure spikes common in turbo, supercharger, and high-rpm applications.