#4flare/#3flare Union

The #4flare/#3flare Union by AEROQUIP is a precision hydraulic adapter designed for high-pressure fluid systems in performance vehicles and heavy-duty automotive applications. This adapter bridges two different flare sizes—#4 and #3—making it essential for custom fuel, oil cooling, and brake line configurations where size transitions are necessary. Whether you're building a modified engine bay, upgrading a fuel system, or integrating auxiliary cooling circuits, this compact union delivers the reliability that serious mechanics and engine builders demand.

AEROQUIP's #4flare/#3flare Union features female flare fittings on both ends, allowing seamless connection between #4 and #3 SAE flare hose or tube specifications. The brass construction provides excellent corrosion resistance and thermal stability under high-pressure conditions typical in race engines and modified drivetrains. Its compact footprint—measuring 2.3 by 1.1 by 3.7 inches—fits tight engine compartments without requiring extensive re-routing, while the minimal weight of 0.04 lbs keeps overall system mass negligible. The flare design ensures leak-free connections when properly torqued, eliminating the need for ferrule adjustments and reducing maintenance headaches in critical cooling and fuel delivery systems.

This union is ideal for fabricators, performance mechanics, and restoration specialists working on custom hydraulic circuits where off-the-shelf hose assemblies won't fit. Common applications include remote oil cooler installations, auxiliary fuel system configurations, and brake line modifications on street rods and track vehicles. When installing, ensure both flare ends are clean and properly aligned before tightening; use two wrenches to prevent twisting the adapter body and damaging the flare seats. AEROQUIP's reputation for durability makes this adapter a reliable choice for applications requiring consistent pressure ratings and vibration resistance in demanding automotive environments.