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Fastener Material Guide

Quick reference chart to common materials used in automotive fasteners. Specifications provided by Automotive Racing Products (ARP). A brief explanation/description of the materials is provided below this chart.

Material Used by ARP? Yield Strength (psi) Tensile Strength (psi) Used For
Grade 5 No 90,000 120,000 Accessory bolts and studs
Grade 8 No 120,000 150,000 Accessory bolts and studs
Stainless 300 Yes 140,000 170,000 Head studs, Accessory bolts/studs
ARP Custom 450 Yes 150,000 180,000 Head bolts, Accessory bolts
8740 Chrome Moly Yes 160,000 190,000 Connecting rod bolts, Head and main studs/bolts
A286 Yes 170,000 200,000 Head bolts, Connecting rod bolts
ARP 2000 Yes 180,000 215-220,000 Connecting rod bolts
L19 Yes 200-230,000 230-260,000 Connecting rod bolts
Iconel 718 Yes 190-210,000 220-240,000 Connecting rod bolts
Custom Age 625+ Yes 235-255,000 250-280,000 Head bolts, Connecting rod bolts
ARP 3.5 Yes 230-250,000 250-280,000 Connecting rod bolts
Aermet 100 Yes 258,500 300,000 Connecting rod bolts

Material Explanations

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. This material is specially polished using a proprietary process to produce a beautiful finish.

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 the heat treatment. (A standard ARP® practice). Typically, chrome moly is classified as a quench and temper steel that can be heat treated to deliver tensile strengths between 180,000-210,000 psi.

ARP 2000

An Exclusive “Hybrid-Alloy” developed to deliver superior strength and better fatigue properties. While 8740 and ARP® 2000 share similar characteristics, ARP® 2000 is capable of achieving clamp loads in the 215,000-220,000 psi range. ARP® 2000 is used widely in short track and drag racing as an upgrade from 8740 chrome moly for both steel and aluminum connecting rods. At this strength level, stress corrosion and hydrogen embrittlement are typically not a problem, provided care is taken during fastener installation.


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 or ARP® 2000, 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 ARP® 2000. 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.


With a typical tensile strength of 280,000 psi, Aermet 100 is a fairly new martensitic super-alloy that is stronger and less expensive than the super-alloy austenitic materials that follow. Because Aermet 100 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 the other high strength steels in its resistance to stress corrosion, it must be kept well oiled and not exposed to moisture.


This is a nickel based material that is in the high temperature, super-alloy class, and 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.

ARP® 3.5 (AMS5844)

While similar to Inconel 718, these super-alloys are found in many jet engines and aerospace applications where heat and stress attack the life of critical components. The high cobalt content of this alloy, although extremely expensive, delivers a material with superior fatigue characteristics and a 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, such as: Formula 1, Winston Cup, and CART applications.


This newly formulated super-alloy demonstrates superior fatigue cycle life, tensile strength, and toughness. With complete resistance to atmospheric corrosion and oxidation it sees many uses. 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.

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