#4 to #3 Flare Seal Reducer

The #4 to #3 Flare Seal Reducer is a precision aluminum adapter fitting designed to bridge incompatible AN (Army-Navy) hydraulic line connections in high-pressure fuel, oil, and cooling systems. As a mechanic working with modified engines and custom fuel systems, you'll recognize this adapter as essential when downsizing from larger #4 AN ports to smaller #3 AN male connections. This fitting solves a common problem: when upgrading fuel rails, carburetors, or aftermarket manifolds, port sizes rarely align perfectly with existing lines. The A-1 PRODUCTS Flare Seal Reducer eliminates the need for custom hose fabrication or bulky adapter cascades.

Machined from aerospace-grade aluminum and finished in vibrant blue anodize, this straight adapter maintains structural integrity under high pressure while resisting corrosion in engine bay environments. The female #4 AN port accepts standard flare-seal hoses, while the male #3 AN outlet threads directly into fuel blocks, carburetors, or gauge ports without additional fittings. Blue anodize coating provides both visual identification and protection against oxidation—critical for reliability in fuel system applications where even microscopic contamination compromises flow and accuracy. The compact 2.85-inch length minimizes dead space in tight engine compartments, and at just 0.03 lbs, adds negligible weight to your build.

This adapter is indispensable for custom carb tuning, EFI conversion harnesses, and performance fuel system consolidation. Street rodders, drag racers, and daily-driver modifiers benefit most when installing modern fuel management systems onto vintage engines or when swapping aftermarket fuel rails that use downsized ports. Installation is straightforward: hand-tighten the #4 flare connection, then torque the #3 male outlet to your manifold or block fitting spec. Verify all connections with a pressure test before ignition—proper AN fitting seals depend on clean threads and correct torque. Compatible with all standard AN hydraulic hoses rated for your fuel type and system pressure.