8AN Straight Thread O-Ring Port Plug Clear

The 8AN Straight Thread O-Ring Port Plug Clear from REDHORSE PERFORMANCE is an essential fitting for any serious engine builder or hydraulic system technician managing fuel, coolant, or fluid lines in high-performance applications. This port plug seals unused AN ports on adapters, manifolds, and fuel rails—preventing fluid leakage, contamination, and pressure loss in precision-engineered fuel systems, transmission coolers, and turbocharger circuits. Whether you're fabricating a custom fuel injection setup, upgrading to a larger capacity fuel system, or converting to aftermarket fuel pressure regulators, this straight thread O-ring port plug delivers reliable sealing at critical junctures where leaks compromise both performance and reliability.

Designed to the 8AN (5/8-inch-18 UNF) straight thread standard, this plug features a precision-machined body with an integrated O-ring seal that creates a leak-proof closure under sustained pressure. The clear polycarbonate or translucent construction allows visual inspection of port cleanliness and fluid condition without removal—a feature that saves diagnostic time during troubleshooting or pre-start system verification. The straight thread configuration (as opposed to flared) simplifies installation in tight engine bay spaces and integrates seamlessly with modern adapter designs common in LS swap projects, EFI conversions, and fuel system modernization. Weighing just 0.07 pounds, the compact 2.8 x 1.15 x 3.8-inch profile fits snugly into crowded fuel rail and manifold assemblies without adding bulk or requiring custom bracketry.

This port plug suits engine builders, fuel system integrators, and transmission cooler installers working with 8AN-threaded components—especially those managing multiple fuel rails, auxiliary coolant loops, or turbo feed-and-return circuits where unused ports must be sealed to maintain system integrity. It pairs perfectly with REDHORSE Performance adapters, braided hose assemblies, and manifold kits in street rods, race cars, vintage restorations, and modern performance vehicles running custom or turbocharged powerplants. Installation is straightforward: hand-tighten or torque lightly to secure; the O-ring does the sealing work, eliminating the need for PTFE tape or sealant compounds that degrade under heat and pressure cycles.