The ARP VQ37VHR L19 Head and Main Stud Kit for the Nissan 370z and Infiniti G37.
The L19 head studs were produced due to head lift issues at high WHP where additional clamping force is needed. While standard ARP head studs can be torqued down to 65-70ft/lbs, these ARP made with 262,000psi tensile strength L19 steel can be torqued down to 90-95 ft/lbs easily, without breaking the stud. These are a direct drop in replacement, and require no special block modifications or machining.
ARP recommends the use of main studs over bolts whenever possible for several key reasons. First is the ability to obtain more accurate torque readings because studs don’t “twist” into the block. All clamping forces are on one axis. By the same token, there is less force exerted on the block threads, which contributes to improved block life (very critical on aluminum blocks). Finally, there are factors of easier engine assembly and proper alignment of caps every time.