2.5 Filler Cap & Bung - Weld-In Steel

The MEZIERE 2.5 Filler Cap & Bung - Weld-In Steel (PN6501) is a heavy-duty cooling system component designed for custom automotive fabrication and engine cooling modifications. This weld-on bung and cap kit serves as a secure access point for radiator fills, overflow systems, and coolant reservoirs on performance and custom-built vehicles. Built for permanent installation, this assembly combines durability with functionality, making it essential for builders, fabricators, and performance enthusiasts who demand reliability in high-heat environments.

This kit features a robust steel bung with a 2.5-inch opening diameter and an aluminum threaded cap, engineered to create a pressure-sealed connection when properly installed. The weld-on design provides a permanent, vibration-resistant mounting solution that eliminates the risk of loosening during engine operation or under thermal cycling stress. The natural finish steel bung withstands extreme temperatures and cooling system pressures, while the threaded aluminum cap allows tool-free access for coolant checks and refills. At just 0.51 lbs, the compact assembly (3.5 x 1.55 x 3.95 inches) integrates seamlessly into custom cooling loops and radiator designs without adding significant bulk or weight.

Engine builders, fabricators, and custom car enthusiasts benefit most from this product when constructing bespoke cooling systems that demand reliability and longevity. Installation requires welding the bung directly onto radiator or tank walls—a one-time operation that creates an unyielding mechanical bond superior to threaded or flanged alternatives. This weld-in bung excels in race applications, restomod projects, and high-performance builds where standard filler necks are unavailable or incompatible with custom designs. Verify your opening diameter matches the 2.5-inch specification and ensure proper TIG or MIG welding technique for optimal results and long-term leak-free performance.