4AN Flare Cap Nut 2 Piece Blue

The 4AN Flare Cap Nut 2 Piece Blue from REDHORSE PERFORMANCE is a critical component for any serious automotive fuel system upgrade or custom fuel line installation. Designed for -4 AN (automotive negative) hose fittings, these cap nuts seal the flared end of your fuel lines with precision-machined reliability. Whether you're building a custom fuel delivery system for a high-performance engine swap, installing aftermarket fuel injectors, or setting up fuel pressure monitoring on a modified vehicle, these cap nuts ensure leak-free connections that withstand elevated fuel system pressures.

Constructed from durable materials engineered to resist corrosion and thermal cycling, the 4AN Flare Cap Nut features a two-piece design that simplifies installation and removal compared to integrated assemblies. The blue anodized finish provides both aesthetic appeal and a protective oxide layer that guards against oxidation in engine bays and fuel tank compartments. The flare cap nut threads onto the fitting body with a hex-head design that accommodates standard wrenches, allowing for proper torque application without over-tightening that could damage the delicate flared seat. This two-piece configuration makes these nuts ideal for field replacement or system troubleshooting without requiring complete line disassembly.

Professional mechanics and performance enthusiasts rely on -4 AN cap nuts when upgrading fuel systems on turbocharged, supercharged, or naturally aspirated builds where fuel pressure exceeds factory specifications. These components work seamlessly with aftermarket fuel rails, surge tanks, and custom manifold fuel distribution blocks. The blue color coding helps technicians identify -4 AN systems at a glance, reducing assembly errors during complex fuel system installations. Whether you're completing a weekend project or managing a full engine bay overhaul, having quality 4AN Flare Cap Nuts on hand ensures your fuel delivery remains pressurized and leak-free under demanding conditions.