ARP 245-4312 High Performance 8740 Head Stud Kit 12-Point

The ARP 245-4312 High Performance Series Head Stud Kit is engineered for demanding performance applications where cylinder head clamping integrity is critical. Manufactured from premium-grade 8740 chrome moly steel alloy—rated superior to aircraft quality—each stud is vertically rack-heat-treated to a nominal 200,000 psi, ensuring complete and even heat penetration throughout the material.

After heat treatment, every stud is centerless ground through approximately ten precision passes to achieve near-perfect concentricity. Threads are then rolled after heat-treat, delivering up to ten times greater fatigue strength compared to studs threaded before heat treatment—a common but inferior industry practice. The result is a stud that provides exceptional alignment: cylinder heads and gaskets glide into position with no binding or misalignment.

Key Features:

• Premium 8740 chrome moly steel alloy construction
• Heat-treated to 200,000 psi for maximum strength
• Centerless ground for superior concentricity and straightness
• Thread rolled after heat-treat for ~1,000% better fatigue resistance
• 12-point head design for reduced wrenching clearance
• Wide-area flanged head eliminates the need for valvetrain removal during retorquing
• Undercut short studs equalize stretch between stud lengths for consistent clamping force
• Hardened, parallel-ground washers included for even load distribution and accurate torque readings
• Helps compensate for head gasket compression, reducing the risk of blown gaskets
• ARP part number stamped on each stud for quality assurance

Why Studs Over Bolts?
For most performance and racing applications, head studs are the preferred fastener. When torquing a head bolt, the fastener is simultaneously twisted and stretched—reacting to two forces at once. With a properly installed stud (finger-tight, never cranked), torque is applied only to the nut, stretching the stud purely on the vertical axis. This produces more accurate, consistent clamping force across the entire cylinder head. Undercut shorter studs are designed to stretch at a rate comparable to longer standard-shank studs, providing uniform load distribution. Always re-torque after initial engine run-in to account for head gasket compression set.

The ARP 245-4312 is a favorite of professional engine builders in all forms of motorsport competition and is backed by ARP's zero-defect, zero-failure quality standard.