[SVXRide]

11.9 =

Ultimate Tensile strength of 1100 MPa (159,500 psi)

Yield Tensile Strength= 990 MPa (143,550 psi)

During engine assembly or maintenance, a bolt must be installed by torquing it into place. Due to the head bolt’s design, it has to be rotated into its slot in order to engage the threads and secure it into place. This process creates both twisting force and a vertical clamping force, which means that when the cylinders within the engine’s combustion chamber begin accumulating load, the bolt will both stretch and twist. Because the bolt has to react to two different forces simultaneously, its capacity to secure the head is slightly reduced and it forms a less reliable seal in high-powered engines.

By contrast, a head stud can be tightened into place without any direct clamping force applied through the tightening. A stud can be threaded into a slot up to “finger tightness,” or the degree to which it would be tightened by hand. Afterward, the cylinder head is installed and a nut is torqued into place against the stud. The nut torque provides the clamping force, rather than the torque of the fastener itself, and the rotational force is avoided entirely. Because the stud is torqued from a relaxed state, the pressure from the nut will make it stretch only along the vertical axis without a concurrent twisting load. The result is a more evenly distributed and accurate torque load compared to that of the head bolt. This ultimately translates into higher reliability and a lower chance of head gasket failure.

and a little bit more....

Application:
Street/Race
ARP 154-3603 Cylinder Head Bolt Kit
Fits 351W Ford V8 with Edelbrock heads 60259, or 60379.
ARP's "High Performance" series cylinder head bolts feature a reduced wrenching hex or 12-point head and a wide area flanged head that eliminates the need for valve train removal to facilitate cylinder head retorquing. All High Performance Series bolts are rated 180,000 psi tensile strength (which is 15% stronger than Grade 8) and all sets include hardened steel parallel-ground washers.
Available with hex heads only.
ARP 154-3603
• ARP's "High Performance" bolts deliver superior strength and are rated at 180,000 psi
• Cold forged and heat treated
• Ideal for all high performance applications
• Reduced hex size for more clearance around valve train components
• Application specific
Last Updated: 2010-01-11 19:02:37