#4 Port Plug w/ Socket Hex

The #4 Port Plug with Socket Hex from FRAGOLA is an essential fitting for custom fuel system builds, cooling loops, and hydraulic line assemblies where port management and flow control demand precision engineering. Whether you're fabricating a bespoke fuel rail, adapting high-performance cooling circuits, or designing aftermarket suspension components, this plug seals unused ports cleanly while maintaining system integrity under pressure. Mechanics and fabricators rely on FRAGOLA's reputation for leak-free, durable fittings that stand up to repeated service cycles and thermal cycling without degradation.

Constructed with a socket hex head design, this #4-sized plug delivers a solid mechanical seal without relying on thread tape or sealant compounds, reducing installation time and eliminating contamination risk in critical systems. The hex socket allows controlled torque application using standard Allen wrenches, ensuring repeatable, uniform pressure without stripping fasteners—critical when working on aluminum manifolds or composite billet components. FRAGOLA's precision-machined construction guarantees dimensional consistency across production runs, meaning thread engagement and sealing surfaces perform identically whether you're on your first build or your fiftieth modification project.

This fitting excels in race-spec fuel systems, LS-swap custom builds, and EFI retrofits where unused carburetor bosses or excess port openings require blanking without bulk or weight penalty. Installation is straightforward—clean the port, apply controlled torque with a properly sized hex key, and verify pressure-hold with your system pressurized. The compact 1.4-inch length and minimal 0.01-pound weight make it ideal for engine bay real estate constraints, and its socket hex design pairs seamlessly with metric or SAE tool sets found in any serious fabricator's workshop.