Designed and manufactured by Heli-Coil to provide specific and unique benefits to high-temperature, high-performance spark plug applications.
Heli-Coil spark plug screw thread inserts are manufactured from 18-8 round stainless steel wire formed into a 60° diamond-shaped wire. This cold-worked wire, which has a tensile strength of 200,000 PSI, is wound into a helical coil with a driving tang and notch to remove the tang after the insert is screwed into the Heli-Coil tapped hole.
In its free state, the insert is larger in diameter than the tapped hole. Once installed, the insert assumes the configuration of the tapped hole. The resulting outward spring-like action anchors the insert in place. The Heli-Coil spark plug insert becomes an integral part of the cylinder head, providing high-strength threads which exceed in surface smoothness, hardness, and accuracy any threads tapped in any material.