12 Piece Header Bolt Kit FOR SBC 3/8-16 x 1.00 Black Grade 8 Steel, Compact 5/16 Hex Flange Head, Black Phosphate Coated, Corrosion Resistant, Fits Small Block Chevy V8 265 283 302 305 307 327 350 400

This 12-piece header bolt set is engineered for Small Block Chevy applications where strength, fitment, and installation access are critical. Manufactured from heat-treated 42CrMo alloy steel and built to Grade 8 specifications, these bolts deliver consistent clamping force in high-heat, high-vibration exhaust environments. The compact 5/16 inch hex head design provides a key advantage during installation, allowing improved access in tight header clearance areas where larger bolt heads can interfere with tubes or tools. This makes them especially effective for block hugger headers, tight engine bays, and performance builds where space is limited. Each bolt features an integrated flange design that eliminates the need for separate washers while evenly distributing clamping load across the header flange. This helps improve gasket sealing and simplifies installation by reducing hardware complexity. A corrosion-resistant black phosphate and blackened coating, tested to ASTM B117 standards, provides protection against rust while maintaining a clean, low-profile appearance in the engine bay. The finish is designed for durability in real-world driving conditions, including repeated heat cycles and exposure to the elements. For proper installation, torque to 25–30 ft-lbs using anti-seize lubricant. Recheck after the initial heat cycle and periodically thereafter to maintain optimal sealing performance. As with all header installations, consistent clamping force is critical to preventing leaks over time. This 12-piece kit is designed for Small Block Chevy engines including 265, 283, 302, 305, 307, 327, 350, and 400. These engines typically use 12 header bolts. Applications requiring 16 bolts, such as certain big block or alternative platform engines, should use the corresponding 16-piece kit. Ideal for muscle cars, restorations, street rods, and performance builds, this header bolt set provides a reliable fastening solution with the strength, fitment, and access required for proper installation.

• GRADE 8 STEEL STRENGTH – Manufactured from heat-treated 42CrMo alloy steel and built to Grade 8 specifications for reliable clamping under high heat and vibration. Designed for performance exhaust systems and demanding installs.
• COMPACT 5/16 HEX HEAD – Smaller hex head design allows improved access in tight header clearance areas where standard bolts are difficult to reach. Ideal for block hugger headers and confined engine bays.
• INTEGRATED FLANGE DESIGN – Built-in flange distributes load evenly across the header flange, eliminating the need for separate washers while improving sealing and simplifying installation.
• BLACK PHOSPHATE COATING – Corrosion-resistant black phosphate and blackened finish tested to ASTM B117 standards helps resist rust while maintaining a clean, low-profile engine bay appearance.
• PROPER TORQUE RETENTION – Designed to maintain clamping force through repeated heat cycles. Recommended torque is 25–30 ft-lbs with anti-seize. Recheck after initial heat cycle and periodically for best results.