#4 Male to 8mm x 1.25 Male Str Adapter

The #4 Male to 8mm x 1.25 Male Str Adapter is an essential hydraulic and pneumatic fitting for custom fuel, oil, coolant, and brake system plumbing in performance vehicles and engine builds. This straight adapter bridges two different port sizes and thread standards, making it indispensable when upgrading fuel systems, turbo setups, or modifying cooling circuits where Russell fittings are specified. Whether you're fabricating a custom fuel rail, installing an external oil cooler, or running remote catch cans, this adapter provides a leak-free transition between dissimilar connection points that factory harnesses cannot accommodate.

Manufactured by Russell, a trusted name in performance plumbing for decades, this adapter features a #4 SAE male port (common in fuel system work) transitioning to an 8mm x 1.25 metric male thread, enabling compatibility across both SAE and metric-equipped components. The straight configuration eliminates bends and reduces turbulence compared to elbow fittings, improving flow efficiency in high-pressure fuel delivery systems and closed-loop cooling applications. Russell fittings are engineered to withstand sustained pressure cycling without thread galling or seal degradation, critical when reliability under boost or sustained RPM is non-negotiable.

Mechanics and fabricators building stroker engines, forced induction kits, or engine bay modifications frequently reach for this adapter when OEM fuel lines or cooling paths require upsizing or rerouting. It pairs seamlessly with Russell hose, fittings, and component ecosystems, ensuring proper torque spec and thread sealant compatibility throughout your plumbing system. Weighing just 0.06 lbs, it adds negligible mass while providing the precision fit and pressure rating your investment in engine modifications demands—order now for your next project build.