A Look Inside ARP Bolts and What Makes Them Better

The first step to creating a successful business is to identify a public need. Then, you’ve got to fill it.

That’s exactly what racing enthusiast Gary Holzapfel did back in 1968 when he noticed friends and fellow racers succumbing to bolt-induced engine failure: He put his background in fastener manufacturing to use and developed a solution. Soon, Holzapfel began making race-quality fasteners with aerospace technology, and ARP was born.

ARP bolts, nuts and studs begin life as coils of top grade steel.


All of ARP fastener manufacturing is done in-house at a Southern California facility. The process starts with wire coils and ends with fasteners, nuts and bolts that are superior to what is widely considered aircraft quality. ARP’s fasteners are built to withstand serious racing, have higher tensile strengths and can survive higher stresses than most aircraft fasteners will ever see.

The process is simple, but more precise than those used for the bolts you’d find at the hardware or aircraft surplus store: First ARP works with their steel suppliers to get the best grade of steel. While steel essentially comes in four grades, ARP uses only the top two (aircraft grade steel is generally only a tier-two material—not up to ARP’s standards). The original line, still produced, is the ARP2000 line, and it exhibits a whopping 220,000-psi tensile strength. But that isn’t even the peak strength of ARP products: new to the lineup, ARP’s Custom Aged 625+ hardware boasts an even-higher tensile strength of 260,000 psi—when you’re boost numbers are climbing, these head studs are a must!

Here you can see a coil feeding into a cold header machine. No additional heat is used in this process.
The cold heading process takes coil wire (L) and forms it into a basic bolt head (R). Four stations are needed to get the coil wire into the necessary form for the bolt making process.
Each batch of ARP bolts is put through rigorous testing before being packaged for shipping. This Instron unit pulls the bolts apart and then registers the force needed to make them yield and break. Bolt stretch and other factors are checked here to ensure your bolts are perfect for your high-power needs.

When the steel arrives, it’s a coil of raw steel wire and looks like a round bar. This steel wire then undergoes one of two processes: cold or hot heading. Contrary to the name’s implication, cold heading is done at room temperature; meanwhile, hot heading is a tad more literal. (It’s not some angry guy yelling at the parts as they wiz down the line!) Instead, the steel is heated to a glowing state to facilitate the forming of complex shapes and/or tougher-than-average (for ARP) alloys. This is just one of the many steps it take to produce the bolts that will keep your race engine alive—even under the most extreme conditions.

All of ARP fastener manufacturing is done in-house at a Southern California facility. The process starts with wire coils and ends with fasteners, nuts and bolts that are superior to what is widely considered aircraft quality.

After forming the basic bolt, stud or nut, with threads, heads and body diameters to suit the application, the stock is sent to ARP’s in-house heat-treat facility and then to shot peening. Heat-treating gives the bolts strength without brittleness, while shot peening further improves the strength and durability.

All ARP products are then random batch tested for quality. Once they’ve passed the grade, they’re packaged up and shipped out to motorsport enthusiasts around the world.

Yep, the race goes on, often because ARP helped keep the heads on and the rod spinning.  DW

Here you see an ARP head stud kit being installed on a Ford 7.3l diesel.
Hot heading involves heating the steel blanks to a precise, red-hot temperature and then putting tons of pressure to form the heads. This process is used for more complicated bolt head designs.
Bolts are sent to the heat-treat ovens to get the correct hardness—not too soft and not too brittle. This BeaverMatic is a hottie and turns soft steel into hard nuts and bolts.

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