ARP Diesel Custom Age 625+ Head Stud Kit 247-4205 Cummins 5.9L 12V '89-'98 CA625+

ARP
head studs begin by being placed vertically into special racks and
precisely heat-treated. This procedure ensures complete heat penetration
and is far superior to those lower quality studs from other
manufacturers who just place the pieces in a basket. Head studs then
move to a centerless grinding process to ensure that they are perfectly
concentric. As many as ten separate machining steps are required to
achieve this level of accuracy. The thread rolling operation is also
done after the heat-treatment, which gives them about 2000% (that’s 20
times) better fatigue strength than lesser 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
upgrade the overall external integrity. Finally, a metal finishing
process is also performed in-house with a durable black oxide coating
applied for improved corrosion resistance.