ARP Head Studs (EJ20, EJ25)

ARP2000 is an alloy steel that can be safely heat treated to a higher level, producing a greater strength material than 8740. While 8740 and ARP2000 share similar characteristics - ARP200 is capable of achieving a clamp load at 220,00 psi. ARP2000 is widely used in short track and drag racing as an up-grade from 8740 chrom moly in both steel and aluminum rods. Stress corrosion and hydrogen embritlement are typically not a problem, providing care is taken to protect the parts from moisture and the parts are kept well-oiled.

What exactly is ARP2000 and how does it compare to 8740 and 4340?

ARP2000 is a heavily alloyed martensitic quench and temper steel. It has excellent stability at high temperatures. But most important, ARP research discovered that in addition to temperature stability it has excellent notch toughness in the higher strength ranges and is alloyed to be tempered to the Rockwell C45/47. 8740 and 4340 can be tempered to the same hardness. But the tempering temperature would yield material in the temper brittle zone (between 500* and 700* F), producing significant notch sensitivity. ARP2000 is tempered above that temperature range and has a strength between 200,000 and 220,000 psi.

Following the basic shaping, material is heat-treated to desired levels. This crucial process is done entirely in-house to assure total quality control. ARP uses special vertical racks to hold each piece individually and assure complete 360° penetration. This is far superior to commonly-used methods of dumping items into a large bin and batch-treating.

The thread rolling operation (to MIL-S-8879A Specifications) is done after heat-treat, which accounts for a fatigue strength up to ten times higher than fasteners which are threaded prior to heat-treat.

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