The chart shows typical results of measuring ten cycles of torquing to the desired setting, loosening the fastener, and retorquing. The amount of preload scatter between the various fasteners lubricants is quite evident.

When it comes to the fasteners themselves, there’s a lot more than meets the eye. You could be looking at two heads studs that for all accounts look the same, but there are dramatic differences in how they’re made and how strong they are. For example, the 8740 chrome moly steel used to make the majority of studs comes in four grades. “Aircraft” quality is only number 2 on the list, whereas ARP uses only the top grades. Then there’s heat-treating. Some manufacturers toss a batch of studs into a basket and shove it into the furnace. ARP, on the other hand, has built special racks that hold each stud vertically and apart so true 360° penetration can be achieved.

ARP also centerless grinds each stud to make sure that it’s concentric. And, finally, the threads are formed after heat-treating. This results in a much higher fatigue strength when compared to studs that are machined when the metal is softer, before heat-treat. Bottom line, it costs more to make studs in this manner, but it also results in a far superior product that can ensure long-term engine reliability. ARP head studs are also hex-broached, which makes them easier to install and remove.

Most ARP studs are made of heat-treated 8740 chrome moly that has a tensile strength of 200,000 PSI. They are more than adequate for the majority of applications. But when extreme combustion pressures come into play, ARP advises the use of special studs made from materials such as their proprietary ARP2000, L19, Custom Age 625+ and other exotic alloys that go up to 300,000 PSI.

You won’t find these special applications in ARP’s catalog, so racers are invited to call toll-free (800-826-3045) for assistance. What’s more, if a particular fastener is not available, ARP can make it. A large portion of the company’s business comes from engineering, designing and manufacturing fasteners for special applications.

ARP firmly believes in supporting Sportsman drag racers, and the company has an NHRA Major Sponsorship program for everything from Stock Eliminator to Top Alcohol Dragsters for use of ARP head bolts or head studs.

As a final note, ARP is proud that every manufacturing operation from forging through heat teat, machining and finishing is done in-house at the firm’s facility in Santa Paula, CA (packaging, warehousing and shipping is done out of their facility in nearby Ventura, CA). Their quality control is second to none, as the company is both ISO-9001 and AS9100 certified. And above all, it’s a company founded on racing and dedicated to helping its customers reach the winner’s circle.