ARP Hardware Materials 101

ARP Hardware Materials 101

Anytime that you are upgrading your engine, adding power, increasing boost, etc, it is a MUST to upgrade the fasteners holding your engine together. ARP hardware is an easy choice, with its established motorsport history as well as notorious quality and strength.

However, when purchasing ARP hardware, you may be confused as to which material to choose or which set is the best choice for your application. On our site, we offer three material options, depending on engine and application, starting with ARP2000 and working up to Custom Age 625+. To ease the process of selecting your hardware material, we outline below each ARP material you see on our website, giving explanation as to what it is made from and what applications it is best for:


Strength: Between 200,000 and 220,000 psi

This is the ‘standard’ ARP steel fastener material you will see on our site. ARP2000 is a heavily alloyed steel that receives special heat treatment, known as martensitic quench, and tempering for strength and hardness. This hardware has exceptional stability at high temperatures and excellent notch toughness in higher strength ranges.

ARP2000 is a well-established choice in motorsport and performance applications, as well as standard rebuilds that demand the highest quality components. This hardware is celebrated by engine builders for its high tensile strength and much greater quality than OEM fasteners, meaning it can withstand higher stress and load levels than standard factory hardware without deforming or failing.

Tensile strength is the maximum load that a material can support without fracture when being stretched, divided by the original cross-sectional area of the material, measured in pounds per square inch, often abbreviated to psi.


Strength: Between 220,000 and 270,000 psi

L19 is different from ARP2000 in that it is vacuum sealed, melted alloyed steel with enough chromium and carbon to achieve high hardness. L19 is air-cooled from hardening temperature using a method that does not require an oil quench to achieve full hardness and is tempered to assure full conversion to martensite between 1025°F and 1075°F. ARP’s L19 hardware offers high strength obtained from high tempering temperature.

L19 hardware offers higher tensile strength than ARP2000, meaning it can withstand greater loads and stresses. It is often chosen for high-performance applications where increased fatigue resistance is crucial, such as drag racing and high-boost turbo builds, that experience frequent and severe load cycles.

Custom Age 625+

Strength: Between 260,000 and 280,000 psi

ARP’s Custom Age 625+ is a newly formulated super-alloy which offers superior fatigue cycle life, tensile strength, and toughness. CA625+ also offers complete atmospheric corrosion and oxidation resistance, meaning it is well-suited to handle the various fluids and environmental conditions that it will be exposed to in an engine. CA625+ hardware is celebrated for its high tensile strength and fatigue resistance, making it the ideal choice for demanding, high-performance applications.

Because ARP was the first to develop the manufacturing and testing process for fasteners of these materials, they have perfected it as a high-strength super-alloy, with uniform strength characteristics. This hardware is a must for high-powered, high-stress applications where exceptional strength and reliability are paramount.


Thank you to our friends at Automotive Racing Products for sharing their expansive engineering knowledge with us!

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