ARP 247-4206 Diesel Head Stud Kit

The ARP 247-4206 Diesel Head Stud Kit from XDP lets you upgrade your 3.9L 4BT Diesel engine so it can withstand anything you throw at it. It’s a proven fact that OEM head bolts are the weak link in a diesel engine; especially if the engine has been modified. That’s because most engines are typically assembled from the factory using Torque-To-Yield (TTY) bolts and preloaded to yield and beyond (typically 100-110%). Any increases in combustion pressure can lead to problems like blown head gaskets or catastrophic engine failure. Furthermore because TTY bolts are yielded by design, they should not be re-used.

It is for good reason that virtually every top professional engine builder relies on ARP head studs for their all-out competition powerplants. ARP is the industry leader and builds heavy-duty head studs and fasteners for a wide variety of popular diesel applications. Using head studs instead of standard bolts provides your engine with the clamping force required to keep your cylinder head from lifting due to higher combustion pressures. For the ARP 247-4206 Head Studs, ARP starts with a premium grade ARP2000 alloy that is rated far superior to aircraft quality alloy steels. ARP2000 is an alloy steel that can be safely heat treated to a higher level, producing a greater strength material than Chrome Moly 8740. While 8740 and ARP2000 share similar characteristics, ARP2000 is capable of achieving a higher clamp load at 220,000 psi.

Each stud is first placed vertically into special racks and precisely heat-treated. This ensures complete heat penetration, and the results are far superior to lower quality studs from other manufacturers that just dump pieces in a basket and hope for the best. ARP head studs then travel through a centerless grinding process to ensure that they are perfectly concentric. The thread rolling operation is also done after the heat-treatment, which gives them about 2000% (that’s 20 times) better fatigue strength than studs that are threaded prior to heat-treat. It costs a lot more to do it this way, because it’s tough on tooling, but the results are worth the additional effort. Fasteners are then shot-peened to remove any surface irregularities and improve overall external integrity. A black oxide coating is applied as the final step for long lasting corrosion resistance.