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Nuts and Bolts

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Selecting the optimum material for use in a given application is of paramount importance. That’s why ARP manufactures fasteners from a wide assortment of materials…ranging from popular stainless steel and 8740 chrome moly to exotic alloys that have been developed to handle space travel. You should also know that there are grades within specific alloys. For example, 8740 is available in four grades: 1. SDF (guaranteed seamless and defect free). 2 CHQ (cold head quality). 3. Aircraft. 4. Commercial. ARP uses only the first two (SDF and CHQ), even though they cost more than double “Aircraft” quality. These are the important features that set ARP squarely at the forefront of the industry. Each and every fastener that carries the ARP name is made from the best possible material for the application, carefully heat-treated in-house, and machined to perfection.

STAINLESS STEEL: Ideally suited for many automotive and marine applications because stainless is tolerant of heat and virtually impervious to rust and corrosion. ARP “Stainless 300” is specially alloyed for extra durability. It’s polished using a proprietary process to produce a beautiful finish. Tensile strength is typically rated at 170,000 psi.

8740 CHROME MOLY: Until the development of today’s modern alloys chrome moly was popularly considered a high strength material. Now viewed as only moderate strength, 8740 chrome moly is seen as a good tough steel, with adequate fatigue properties for most racing applications, but only if the threads are rolled after heat treatment, as is the standard ARP production practice. Typically chrome moly is classified as a quench and temper steel, that can be heat treated to deliver tensile strengths between 180,000 and 210,000 psi.

ARP2000: An exclusive, hybrid-alloy developed to deliver superior strength and better fatigue properties. While 8740 and ARP2000 share similar characteristics—ARP2000 is capable of achieving clamp loads in the 215,000-220,000 psi range. ARP2000 is used widely in short track and drag racing as an up-grade from 8740 chrome moly in both steel and aluminum rods. Stress corrosion and hydrogen embrittlement are typically not a problem, providing care is taken during installation.

L19: This is a premium steel that is processed to deliver superior strength and fatigue properties. L19 is a very high strength material compared to 8740 and ARP2000 and is capable of delivering clamp loads in the 230,000-260,000 psi range. It is primarily used in short track and drag racing applications where inertia loads exceed the clamping capability of ARP2000. Like most high strength, quench and temper steels—L19 requires special care during manufacturing to avoid hydrogen embrittlement. This material is easily contaminated and subject to stress corrosion. It must be kept well-oiled and not exposed to moisture.

AERMET 100: With a typical tensile strength of 280,000 psi, Aermet 100 is a new martensitic super-alloy that is stronger and less expensive than the super-alloy austenitic materials that follow. Because it is capable of achieving incredibly high clamping loads, it is ideal for short but extreme environments like top fuel, funny car and some short track applications. Although Aermet 100 is a maraging steel that is far superior to other high strength steels in its resistance to stress corrosion, it must be kept well-oiled and not exposed to moisture.

INCONEL 718: A nickel based material that is in the high temperature, super-alloy class, it is found to be equally suitable in lower temperature applications. This material delivers tensile strengths into the 220,000 psi range and exhibits improved fatigue properties. Best of all, Inconel 718 is completely immune to hydrogen embrittlement and corrosion.

ARP3.5 (AMS5844): While similar to Inconel 718, these super-alloys are found in many jet engine and aerospace applications where heat and stress attack the life of critical components. The high cobalt content of this alloy, while expensive, delivers a material with superior fatigue characteristics and typically tensile strength in the 270,000 psi range. The immunity to hydrogen embrittlement and corrosion of these materials is a significant design consideration. These materials are primarily used in connecting rods where extremely high loads, high RPM and endurance are important factors—Formula 1, Winston Cup and CART applications.

CUSTOM AGE 625+: This newly formulated super-alloy demonstrates superior fatigue cycle life, tensile strength and toughness—with complete resistance to atmospheric corrosion and oxidation. ARP is the first to develop manufacturing and testing processes for fasteners with Custom Age 625+. Best of all it is less expensive and expected to soon replace MP-35 as the material of choice in the high strength, super-alloy field. Typical tensile strength is 260,000 psi.


Material Use? Yield Strength Tensile Strength Used For
Grade 5 No 90,000 psi 120,000 psi Accessory bolts and studs
Grade 8 No 120,000 psi 150,000 psi Accessory bolts and studs
"Stainless 300" Yes 140,000 psi 170,000 psi Accesory bolts and studs, head studs
ARP Custom 450 Yes 150,000 psi 180,000 psi Head bolts, accessory bolts
8740 chrome moly Yes 160,000 psi 190,000 psi Rod bolts, head and main studs and bolts
A286 Yes 170,000 psi 200,000 psi Head bolts, connecting rod bolts
ARP2000 Yes 180,000 psi 215,000-220,000 psi Connecting rod bolts
L19 Yes 200,000-230,00 psi 230,000-260,000 psi Connecting rod bolts
Inconel 718 Yes 190,000-210,000 psi 220,000-240,000 psi Connecting rod bolts
Custom Age 625+ Yes 235,000-255,000 psi 250,000-280,000 psi Head studs, connecting rod bolts
ARP 3.5 Yes 220,000-250,000 psi 250,000-280,000 psi Connecting rod bolts
Aermet 100 Yes 258,000 psi 300,000 psi Connecting rod bolts

SPECIAL NOTE: The U.S. Government has recently implemented new guidelines relating to rating fastener strength. Unless a specific fastener has been tested in a government approved independent lab, manufacturers are enjoined from using a specific rating. Even though, in the case of ARP, the very same equipment and testing procedures are used in-house. Rather than have expensive duplicate tests run on literally hundreds of part numbers. Which would drive the cost of each fastener through the roof, ARP is following approved guidelines by using generalities to describe strength ratings. Please remember that ARP is one of the few firms in the world licensed by the U.S. Government to manufacture MS21250 fatigue rated fasteners and is QPL (Qualified Products Listed). There are few fastener manufacturers in the world with ARPÕs proven reputation for producing quality products.

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