#4 Caps

The #4 Caps from EARLS are essential sealing components for high-performance fuel and fluid systems in automotive applications. Whether you're building a custom fuel injection setup, upgrading your cooling circuit, or assembling a precision hydraulic line network, these caps provide reliable port closure for EARLS adapters and manifolds. Designed for mechanics and enthusiasts who demand leak-free connections under demanding conditions, #4 caps ensure system integrity across temperature and pressure cycling.

EARLS #4 caps feature precision machining and engineered sealing surfaces that prevent fuel weeping and fluid loss in closed-off adapter ports. The compact 1.95 x 0.6 x 3.2 inch profile allows clean integration into tight engine bay layouts while the minimal 0.03 lb weight eliminates unnecessary heft. These caps are manufactured to exacting tolerances, ensuring consistent thread engagement and a secure, vibration-resistant fit—critical factors when working with fuel systems that experience constant vibration and thermal stress during acceleration and sustained high RPM operation.

Ideal for fuel system modifications, turbo fuel rails, custom coolant distribution blocks, and aftermarket manifold assemblies, the #4 Caps are most valuable when configuring multi-port fuel systems or adapting OEM-spec hose runs to custom layouts. Professional builders and weekend fabricators alike rely on EARLS components for system longevity; these caps ensure unused ports remain sealed against contamination and pressure loss. Compatible with all EARLS #4 male ports and adapter fittings, they represent a cost-effective safeguard against costly leaks and downtime.