5/16-24 Large Flange Header Nut (1pk)

The ARP 5/16-24 Large Flange Header Nut is a precision fastener designed for high-performance engine applications where standard fasteners fall short. This 12-point chromoly nut combines superior clamping force distribution with reliable performance under extreme conditions, making it the choice for serious engine builders and technicians working with custom headers and intake manifolds.

The 5/16-24 thread specification delivers the precise pitch and diameter required for critical fastening applications where vibration and thermal cycling demand consistent retention. The large flange design distributes load across a wider surface area, reducing stress concentration and preventing fastener pull-through on softer materials. Chromoly construction provides superior tensile strength and heat resistance compared to standard steel, essential when exposed to engine bay temperatures and repeated thermal expansion cycles. The black oxide finish offers corrosion resistance and a professional appearance while maintaining the integrity of the fastening surface.

This single-pack nut is ideal for engine builders, performance shops, and enthusiasts assembling or rebuilding custom headers, intake systems, or specialized engine components. The 12-point head geometry facilitates tool engagement and reduces the risk of rounding compared to 6-point alternatives, critical when working in tight engine compartment spaces. Whether restoring a classic engine, upgrading a high-performance build, or maintaining precision equipment, the ARP header nut delivers the reliability and strength that serious builders expect from ARP fastener technology.