A one-time use component, most customers choose this option if they don't plan on gaining more Horse Power. When torquing these OEM Head Bolts, they end up stretching, resulting in a one-time use only.

Stronger than the OEM Stretch Bolts. Good for up to 250HP and higher boost applications (have been run up to 40lbs of boost)

XR SERIES 9MM CUSTOM AGE 625 HEAD STUD KIT

XR Series Components are used by the Evolution Racing Team in all their race vehicles. These XR Series 9mm direct replacement head studs are designed for those wanting the ultimate strength for 250-320 horsepower builds.

• Made of proprietary Custom Age alloy and are stronger than any other 9mm stud available anywhere
• These head studs will keep your engines head sealed for the boost pressure required to produce 250-320 horsepower
• Direct replacement 9mm head stud - Easy installation 
• Made from ARP CA-625 alloy - This super-alloy has superior fatigue cycle life, tensile strength and toughness which is rated to 260,000 psi tensile strength. For comparison, a typical 8470 chromoly stud is roughly 170,000 psi 
• More thread engagement into the engine block compared to other studs
• Includes head studs, nuts, and washers