2023
Engine Accessory 114 Kits Include Motor Mount, Alternator Bracket, Water Pump, Front Cover, Fuel Pump, Intake Manifold, Valve Cover, Coil Bracket, Exhaust Header, Thermostat, Distributor Bracket, Oil Pan Driveline 116 Flywheel. . . . . . . . . . . . 116 Flexplate. . . . . . . . . . . . 119 Torque Converter . . . . . 120 Ring Gear. . . . . . . . . . . 121 Bellhousing. . . . . . . . . . 122 Carrier Fasteners . . . . . 123 Rear End Cover. . . . . . . 123 Clutch Cover. . . . . . . . . 124 Pressure Plate . . . . . . . 124 Manual Transmission Case. . . . . . . . . . . . . . . 125 Porsche Transmission Mount. . . . . . . . . . . . . . 125 Auto Transmission Pan 125 Lower Pulley Bolts . . . . 126 Drive Plate . . . . . . . . . . 127 Sprint Car Drive Pins. . . 127 Brake Hat. . . . . . . . . . . 127 Wheel Studs. . . . . . . . . 128 Nascar 133 Speed Studs. . . . . . . . . 133 Speed Nuts. . . . . . . . . . 134 Intake Manifold. . . . . . . 134 Carburetor, drilled. . . . . 135 Alternator. . . . . . . . . . . 135 Header, drilled. . . . . . . . 136 Front Mandrel. . . . . . . . 136 Diesel 137 Cylinder Head Studs. . . 138 Cylinder Head Bolts 139 Rod Bolts . . . . . . . . . . . 139 Main Studs. . . . . . . . . . 140 Harmonic Damper. . . . . 140 Exhaust . . . . . . . . . . . . 141 Valve Cover. . . . . . . . . . 141 Flywheel. . . . . . . . . . . . 142 Flexplate. . . . . . . . . . . . 142 Rocker Pedastal . . . . . . 142 Ring Compressors . . . . 142 Powersports 143 Rod Bolts . . . . . . . . . . . 143 Cylinder Head Studs. . . 143 Cylinder Head Studs. . . 143 Main Studs. . . . . . . . . . 143 Main Bolts . . . . . . . . . . 143 Engine & Accessory . . . 143 Rod Bolts 42 Aftermarket Rods. . . . . . 42 OEM Replacement . . . . . 44 Head Studs & Bolts 58 Cylinder Head Studs. . . . 58 Cylinder Head Bolts 72 Main Studs & Bolts 78 Main Studs. . . . . . . . . . . 78 Engine Case Kits. . . . . . . 82 Main Bolts . . . . . . . . . . . 83 Cylinder Head 86 Rocker Arm Studs. . . . . . 86 Rocker Arm Adjusters. . . 88 Rocker Pedastal Studs . . 89 Valve Cover. . . . . . . . . . . 90 Accessory Studs. . . . . . . 92 Header Collector Bolts . . 93 Header. . . . . . . . . . . . . . 94 Engine Block 96 Oil Pan. . . . . . . . . . . . . . 96 Oil Pump. . . . . . . . . . . . . 97 Front Cover. . . . . . . . . . . 98 Water Pump. . . . . . . . . . 98 Alternator. . . . . . . . . . . . 98 Water Pump Pulley. . . . . 99 Motor Mount. . . . . . . . . 100 Starter . . . . . . . . . . . . . 100 Fuel Pump . . . . . . . . . . 101 Seal Plate. . . . . . . . . . . 101 Accessory Cam Drive. . 101 Intake 102 Carburetor . . . . . . . . . . 102 Air Cleaner. . . . . . . . . . 103 Distributor . . . . . . . . . . 103 Intake Manifold. . . . . . . 104 Carburetor Float Bowl. . 105 Coil Bracket . . . . . . . . . 106 Thermostat Housing. . . 106 Blower (break-away) 107 Blower Pulley. . . . . . . . 107 Engine Components 108 Harmonic Damper. . . . . 108 Square Drive Damper. . 110 Oil Pump Driveshaft . . . 110 Alternator. . . . . . . . . . . 111 Fuel Pump Pushrod. . . . 111 Cam. . . . . . . . . . . . . . . 112 Cam Tower. . . . . . . . . . 113
Terms & Conditions 179 ARP ARP Tech Guide A Brief History. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 The Manufacturing Process . . . . . . . . . . . . . . . . . . 5 Behind the Scenes. . . . . . . . . . . . . . . . . . . . . . . . 10 What ARP Can Do For You. . . . . . . . . . . . . . . . . . . 11 A Tribute to ARP’s Foundations . . . . . . . . . . . . . . . 12 The “Aerospace Quality” Myth . . . . . . . . . . . . . . . 14 Motorsports Fastener Engineering for the Non-Engineer. . . . . . . . . . . . . . . . . . . . . . . . . 18 Recognizing Common Fastener Failures. . . . . . . . 22 Metallurgy for the Non-Engineer. . . . . . . . . . . . . . 24 Custom Fasteners. . . . . . . . . . . . . . . . . . . . . . . . . 31 Material Specifications. . . . . . . . . . . . . . . . . . . . . 33 Glossary of Tech Terms. . . . . . . . . . . . . . . . . . . . . 34 Head Fastener Measurements 36 General Torque Recommendations. . . . . . . . . . . . 37 Proper Fastener Retention. . . . . . . . . . . . . . . . . . . 38 The Importance of Proper Rod Bolt Stretch & Torque . . . . . . . . . . . . . 52 Rod Bolt Length Monitoring Chart. . . . . . . . . . . . . 53 Rod Bolt Stretch & Torque Specs. . . . . . . . . . . . . . 54 Head Studs versus Bolts. . . . . . . . . . . . . . . . . . . . 73 Fasteners by Dimension 144 SAE Bolts 10/24 & 10/32. . . . . . . 145 1/4-20. . . . . . . . . . . . . 146 1/4-28. . . . . . . . . . . . . 147 5/16-18. . . . . . . . . . . . 148 5/16-24. . . . . . . . . . . . 149 3/8-16 Reduced. . . . . . 150 3/8-16 Standard. . . . . . 150 3/8-24 Reduced. . . . . . 151 3/8-24 Standard. . . . . . 151 7/16-14 Standard. . . . . 152 7/16-20 Standard. . . . . 153 1/2-13. . . . . . . . . . . . . 155 1/2-20. . . . . . . . . . . . . 156 Metric Bolts M6 x 1 0. . . . . . . . . . . . 157 M8 x 1 25. . . . . . . . . . . 158 M10 x 1 25. . . . . . . . . . 159 M10 x 1 50. . . . . . . . . . 159 M12 x 1 50. . . . . . . . . . 160 M12 x 1 75. . . . . . . . . . 160 Nuts SAE 12-point . . . . . . . . 161 Metric 12-point. . . . . . . 162 SAE Hex. . . . . . . . . . . . 163 SAE & Nyloc. . . . . . . . . 163 Serrated Flange . . . . . . 164 Self-Locking. . . . . . . . . 164 Washers SAE . . . . . . . . . . . . . . . 165 Metric. . . . . . . . . . . . . . 168 Insert Washers. . . . . . . 169 Weld Bungs . . . . . . . . . 169 Bulk Fastener Bins - 170 Installation Tools 171 Ultra-Torque. . . . . . . . . 171 Rod Bolt Stretch Gauge. . . . . . . . . . . . . . 172 Thread Sealer. . . . . . . . 172 Rod Bolt Extensions . . . 173 Rod Vise. . . . . . . . . . . . 173 Thread Cleaning Chasers . . . . . . . . . . . . 174 Spark Plug Indexer. . . . 174 Ring Compressors . . . . 175 Ring Squaring Tools . . . 176 Oil Pump Primer Kits. . . 176 Apparel 177 Automotive Racing Products, Inc 1863 Eastman Avenue, Ventura, CA 93003 Copyright MCMXC-MMXXIII Automotive Racing Products, Inc. All Rights Reserved. “ARP”, the ARP logo, Wave-Loc, Perma-Loc, ARP2000, ARP3.5 and ARP Ultra-Torque are registered trademarks of Automotive Racing Products, Inc. All other trademarks are property of their respective owners. ARP-bolts.com 800-826-3045
4 A Brief History They say that to be successful you must identify a need and satisfy it. Back in 1968 racing enthusiast Gary Holzapfel saw that many of his friends’ broken engines were caused by fastener failure. At the time, there were no commercially available studs and bolts up to the challenge. So Holzapfel called upon his many years of fastener making experience for a leading aerospace subcontractor and founded ARP® (Automotive Racing Products). In the ensuing years, the firm has grown from what was literally a backyard garage workshop into a highly diversified manufacturer with five operational entities in Southern California with a combined area in excess of 148,000 square feet. These include forging, machining, finishing and packaging/warehousing facilities in Santa Paula and Ventura, California. There is even a unique racing-themed restaurant at the main Santa Paula facility (called “Hozy’s Grill” - which is open to the public). Today, ARP’s product line contains thousands of part numbers, and has expanded to include virtually every fastener found in an engine and driveline. These range from quality high performance OEM replacement parts to exotic specialty hardware for Formula 1, IndyCar, IMSA, NASCAR and NHRA drag racing and marine applications. ARP’s customer list reads like a “who’s who” of motorsports around the world. In the past several years, virtually every major championship on Three generations are now involved in the company – Gary: founder & chairman, Mike: president, Ryan: manufacturing Gary Holzapfel Founder and chairman ARP’s state-of-the-art manufacturing facility in Santa Paula. THE COMPANY
5 the planet has been won with engines prepared by ARP customers. These include Nascar, IndyCar, Formula 1, IMSA, NHRA Top Fuel, Funny Car & Pro Stock, Nascar Xfinity and Camping World Truck Series. And so it goes. ARP works closely with many, many teams as a supplier of engine and driveline fasteners, and has clearly become recognized as “the” preeminent source for serious racers. In addition to its core automotive business, ARP has an Aerospace Division, and is one of the very few companies in the world fully licensed by the United States Government to manufacture MS-21250 fatigue rated fasteners. ARP also manufactures a variety of industrial fasteners on a contract basis, and is known for its ability to promptly provide efficient solutions to problems at hand. The Manufacturing Process In order to ensure optimum quality control, ARP has grown to be exceptionally self-reliant and now controls all aspects of the manufacturing process. All operations are performed Packaging, warehousing and sales operations are handled out of Ventura. Material comes from the mill in large coils...which subsequently will be fed into cold-headers and formed into bolts. THE COMPANY
6 in-house and closely monitored. This is how ARP has been able to establish a reputation for “zero defects” quality throughout the industry. The process begins right at the mill, where ARP orders only premium grade materials including several proprietary alloys. The ever-popular 8740 chrome moly steel, for example, comes from themill in four distinct grades. The lowest is “commercial,” which is followed by “aircraft quality.” ARP uses only the top two grades (SDF and CHQ), which cost twice as much, but provide the foundation for defect-free fasteners. These materials come in bar stock (for studs) and huge coils (for bolts). Most ARP fasteners start off on a cold header, where the high quality wire is cut to length and the head and shank are formed in a multi-stage forging process that contributes to the strength of the overall fastener. A few of our fasteners are cut from bar ARP’s bank of cold-headers can handle material up to 5/8˝ diameter and form bolts in a multiphase operation. Heat-treating is critically important in obtaining the correct tensile strength. Fasteners are placed in special vertical racks to ensure complete 360˚ penetration. An overview of part of ARP’s expansive machining operations. The shop is laid out for optimum efficiency. THE COMPANY
7 stock and hot headed. Following the cold/hot forging, material is heat-treated to desired levels. This crucial process is done entirely in-house to assure total quality control. ARP uses custom vertical racks to hold each piece individually and assure complete 360° penetration. This is far superior to commonly-used methods of dumping items into a large bin and batch-treating. Studs are centerless ground to guarantee concentricity. The thread rolling operation (to MILS-8879A specs) is done after heat-treat, which accounts for a fatigue strength up to twenty times higher than fasteners which are threaded prior to heat-treat. ARP manufactures nuts in a multistep process that begins with raw material being fed into a giant forming device that “blanks” the hex and 12-point nuts and continues with highly sophisticated, atuomatic tapping machines that tap each nut with an accuracy of .001˝ (which is five times higher than the aerospace standard). This ensures an exceptionally close-tolerance fit The Grinding Department is where all studs are centerless ground to ensure that they are concentric and straight. Powerful cold-forging equipment is used to make ARP’s hex and 12-point nuts. Multi-stage dies are employed to precision-form the finished “blanks.” A series of CNC-threading machines are employed by ARP to accurately tap the threads in nuts. Tolerances held are better than aerospace standards. THE COMPANY
8 between the bolt/stud and nut. Metal finishing is also performed in-house at ARP. Operations include black oxide coating of chrome moly or polishing stainless steel to a brilliant luster. Also on the premises is a fully-equipped lab for R&D and quality control. It has everything required to ensure that ARP products measure up to the company’s ultra high standards. Some of the tests that ARP personnel perform on a daily basis include ultimate tensile strength (using a 120,000 lb. capability tensile machine), fatigue cycle (Amsler) and hardness (Rockwell). Visual inspections include use of an optical comparator (to check thread root contour, etc.), fixtured micrometers and microscopic grain flow analysis. The computer-controlled fatigue cycle testers allow ARP to take fasteners to a failure point in millions of cycles – as A bank of CNC machining centers are employed at ARP to perform specialty operations. State-of-the-art EDM technology is used to perform special operations, such as hex-broaching head studs. Fasteners are shot-peened to improve fatigue life. The finishing touch for most chrome moly fasteners is the black oxiding operation. THE COMPANY
9 opposed to the aerospace norm of 65,000 average to 130,000 cycles maximum. This allows ARP engineers to verify the design specifications of each fastener, and prove its ability to provide superior long-term service. Finished products are packaged and warehoused in ARP’s Ventura facility, which is also home to the firm’s customer service, technical and sales office. High powered magnifiers are used to carefully inspect critical components. ARP’s quality control team is relentless! A series of special checking devices are employed to monitor the quality of threads. For every thread size, there is a checking device. Two computer-controlled Instron tensile machines are used to determine the ultimate tensile strength of studs and bolts. ARP has two highly sophisticated Amsler fatigue machines, which test fasteners through millions of cycles. The finished goods are given a protective coating and stored in sealed containers, awaiting packaging. Millions are in stock! THE COMPANY
10 There are a number of important elements in the production of specialty fasteners, not the least of which are materials, design and manufacturing. As you read further into this catalog, you will get a better idea of the extraordinary steps taken by ARP to produce the very finest products of their kind on the market today. The key to success in all areas is personnel. And here’s where ARP’s cadre of highly qualified and dedicated specialists shines brightly. Two valuable resources in the design of ARP products are Russell Sherman, P.E., and up until 2014, Dr. Kenneth Foster. Bothmen have extensive backgrounds in mechanical engineering, metallurgy and stress analysis. Mr. Sherman’s academic credentials are substantial, and real world experience equally impressive. Mr. Sherman has been awarded a fellowship from A.S.M. International, a technical achievement award from Fastener Technology International, and holds a number of fastener patents. (Dr. Foster passed away in 2014. Please read about his contribution to ARP on page 12 – “ARP Foundations” – with tributes to three important members of the ARP team who are no longer with us.) Some of the most valuable work done by Foster and Sherman includes analyzing various aspects of engine, chassis and driveline structural loads, and coming up with solutions to the problems at hand. In this manner, the ARP Research Team is able to continually expand the company’s product line. ARP has added Robert Logsdon to its cadre of consultants. He comes to ARP with vast experience in the area of Metrology, Quality Control, Manufacturing, Acquisition and Configuration Management. Logsdon is a graduate of the U.S. Naval Academy of Metrology Engineering, the DefenseManagement College and U.S. Air Force Institute of Technology. Additionally, ARP has one of the industry’s most After final packaging the kits are placed in storage racks and are ready for order fulfillment. Thousands of SKU’s are warehoused. Components for each kit are placed on the appropriate display cards, sealed and labeled. Through-put has been significantly increased. Robert Logsdon Q.C. Consultant Russell Sherman, P.E. Consulting Engineer Behind The Scenes THE COMPANY
11 complete in-house R&D/QC facilities and a wide variety of testing equipment. ARP also enjoys a solid working relationship with many of the most respected professional engine builders and race teams from the world over – including those involved in Formula 1, IndyCar, IMSA, Nascar, NHRA, IHRA, Lucas Oil Late Model Dirt, World of Outlaws and a host of others. Constant interaction with these racing experts to provide fasteners for a wide variety of competition applications enables ARP to stay on the cutting edge of fastener technology development. You will find ARP fasteners sold by leading performance retailers and professional engine builders around the world. These firms know that ARP fasteners are the standard of the industry, and smart consumers will accept no substitutions. As you can see, all ARP fasteners are proudly made in the USA to the industry’s highest standards. ARP also supports racers through generous contingency awards programs with many racing programs. ARP is a long-time NHRA Major Sponsor. What ARP Can Do For You In addition to manufacturing a comprehensive array of cataloged fasteners for automotive and aerospace applications, ARP thrives on the challenges of developing fasteners to solve unique problems. Racers, Pro Street enthusiasts and street rodders have, over the years, approached ARP about manufacturing special fasteners for unique applications, and the company has responded with innovative solutions. ARP can provide complete R&D services, including metallurgical research, product design, prototype machining and extensive laboratory testing. Moreover, ARP has experience manufacturing fasteners from a wide variety of materials. All work can be performed under the strictest confidence. ARP is well versed in facilitating proprietary research and custom manufacturing for corporations the world over. It is for good reason that ARP is recognized as “The World Leader In Fastener Technology!” See page 31 for more information on our Specials Department. ARP fasteners are prominently featured at leading performance retailers worldwide. THE COMPANY
12 Kenneth Foster Dr. Foster had a Ph.D. in Engineering Mechanics from Cornell University and taught at several colleges. He was formerly the head of Stress & Dynamics at Hughes Aircraft, Space Systems division. He also worked on numerous projects with NASA. Once he began working for ARP, Ken brought all those experiences to bear on the challenges of designing and engineering racing fasteners. Over the years, he was involved in examining all aspects of high-strength fasteners, always figuring out the balance between high-strength, ductility, fatigue and notch sensitivity. Ken was a huge asset to ARP and a friend to all of us here who worked with him. Ken enjoyed a dynamic career as a consulting engineer and valued the relationships he created with colleagues and clients. Ken took great pride in his work and enjoyed sharing his knowledge and expertise with others. A teacher at heart, Ken showed great patience – whether explaining a complicated analytical process to another professional or tutoring neighborhood kids in basic algebra. Ken loved his work and his family, including his beloved wife Connie and their children and grandchildren. Active into his 80’s, Ken was known as the Silver Streak at the high school track. An active community member, Ken was the leader of a prostate cancer support group, offering education and support to numerous men around the world. Ken Foster, PhD, 1932-2014. Consulting Engineer Ken Foster A Tribute to ARP’s Foundations During the past 48 years, ARP has relied on the expertise of three individuals who contributed to our strong technological foundations. Their experience and knowledge covered three core areas that have been critical to ARP’s success at designing and manufacturing the best fasteners in the industry: fastener stresses and engineering, practical use of chassis fasteners and pushing engine fasteners to their limits. We feel it is important to acknowledge these individuals who left their imprints on ARP – everyone who uses our fasteners benefits from the knowledge and experience they imparted before they left us. – Mike Holzapfel President THE COMPANY
13 Carroll Smith Carroll Smith was a design and development engineer, a team manager, driver coach and all-around racing guru. And before that, he was known for his 30+ years of racing experience, driving in SCCA events, as well as on circuits in Europe including the Targa Florio and Le Mans. Among his peers at the Society of Automotive Engineers, he served as a judge for the Formula SAE competition. One of his proudest honors was the Society’s Excellence in Engineering Education award. Carroll Smith was a race engineer and special motorsports consultant with Automotive Racing Products for more than decade. The pages of our catalog bear the mark of his enormous contributions to our efforts. Here at ARP, as elsewhere, Carroll Smith’s mission was simple. He was determined to impart the encyclopedic knowledge of racing and the machinery of racing that he learned during those decades on the world’s racetracks, around those shops and among his engineering peers. He left us at ARP with a significant engineering inheritance. Much of what we now know from Carroll will ensure we remain the world leader in the field of racing fasteners. Carroll Smith passed away at his California home on May 16, 2003, from pancreatic cancer. Smokey Yunick For many years “Smokey” Yunick served as a valued tech consultant and spokesman for ARP. He was a popular host of our Tech Seminars at trade shows, and his knowledge of fasteners was truly astounding. Smokey passed away in 2001, but his wit and wisdom will live on. Smokey never did anything related to racing halfway – he was constantly exploring and learning his entire life. He was fully involved in racing from the mid 40’s through the late 70’s. After that, he worked in his shop everyday, creating new engine designs and solving problems. We chose Smokey to be a spokesman and technical consultant for ARP because of his decades as one of the world’s most innovative and prolific engine builders – and his ability to tell it straight. During his racing years, fastener technology followed the “cut and try method.” He tried going one size larger, he tried aerospace fasteners and he tried fasteners from various companies who claimed expertise. Through those learning experiences, he found that there were no solid solutions. From the day Smokey visited our facilities and talked to our engineers, he realized that he had found what he was looking for: a company that was focused on building the best racing fasteners, with the engineering expertise, raw materials, manufacturing processes and quality control. Smokey was a valued consultant and spokesman until his passing in 2001. Legendary Race Engineer Carroll Smith Hall of Fame Mechanic “Smokey” Yunick THE COMPANY
14 THE “AEROSPACE QUALITY” MYTH In areas from hose ends to engine fasteners the terms “Aerospace material and Aerospace Quality” have become buzz words implying the very best in design, materials and quality control. “It isn’t necessarily so”, says Gary Holzapfel, founder and CEO of Santa Paula, California based ARP, Inc. ARP (Automotive Racing Products) supplies extremely high strength and fatigue resistant threaded engine fasteners to NASCAR, IndyCar, NHRA, IMSA and Formula 1 engine builders and manufacturers. Holzapfel explained his reasons in an interview with Carroll Smith. Smith: “Gary, do you believe that the term “aerospace quality” is over rated in the specialty fastener industry?” “Yes I do. First of all, the term is meaningless. Any AMS (Aerospace Material Specification) material must be matched to the specific application. As an example, some airframe bolts (AN3-20) are legitimate “aerospace parts” and are very well suited for the low stress applications for which they were designed. But with a minimum ultimate tensile strength of 125,000 psi, and a relatively low temperature limit, they would be completely unsuitable for use in a racing engine. We started out in the aerospace fastener business and we understand it. That’s why we’re not in it any longer. What is not generally understood about aerospace fasteners is that the fastener manufacturers do not design the product. The nuts, bolts and studs are spec’d by the airframe or engine designers and put out for bid. As long as the supplier certifies that the product meets the minimum requirement of the specification and it passes the customer’s inspection procedures, low bid wins.” Smith: “Are you implying that the aerospace fastener manufacturers cut corners in order to win contracts?” “No, it’s a matter of manufacturing goals and simple economics. The aerospace market is price dominated. In order to get the contract, the fastener manufacturer’s goal is to meet the specification at the least cost, not to produce the best possible part. This means that they are going to use the least expensive steel and manufacturing processes that will meet the specification. There is nothing wrong with this approach. It certainly does not mean that certified aerospace fasteners are unsafe in any aspect. They will do the job for which they were designed. There is another factor. Airframe and aircraft engine manufacturers design their components to a very high margin of safety. Further, aerospace structures are designed to be “fail safe.” There is a back up or second line of defense for virtually every structural component so that an isolated failure will not lead to disaster. They are also subjected to frequent and rigorous inspections.” Smith: “What’s different about motor racing?” “Quite a lot, really. While the demands for strength, fatigue resistance and quality control can be similar, and the assembly and inspection procedures in racing can be as rigorous as aerospace, in professional racing very few parts are over designed and there are no fail safe features. FASTENER TECH
15 There are no back up provisions for component failure. A failed (or even loosened) nut or bolt in a racing engine means disaster – instant catastrophic failure. An expensive engine is destroyed and a race is lost. That is why random failures are unacceptable in motor racing, and why aerospace standards should be only a starting point. This means that a specialist in the production of high performance engine fasteners must design and manufacture the very best fasteners that can be produced.” Smith: “So where does the production for a new racing fastener begin?” “The design process begins with the customer’s requirements the operating conditions and loads to be expected, the packaging constraints and the weight and cost targets. This allows us to select the optimum material for the part, and to do the initial mechanical design. There is more to material selection than simply choosing the best alloy. It means using only the cleanest and purest steel available, which, in turn, means researching to identify the best and most modern steel mills. It means working closely with the mills both to insure consistent quality and to develop new and better alloys. There are not only a myriad of alloys to choose from; but for each alloy there are several grades of “aircraft specification” steel wire from which fasteners can be made. We believe that only the top (and most expensive) grade – shaved-seamless, guaranteed defect-free – is suitable for racing engine applications. We also believe that samples fromeach batch should be subjected to complete metallurgical inspection.” Smith: “How many alloys do you work with?” “We are currently producing fasteners from at least 10 different steel alloys from 8740 chrome moly to the very high strength chromium-cobalt-nickel alloys such as Custom Age 625+. We also use stainless steel and titanium. With UTSs (Ultimate Tensile Strength) from 180,000 to 270,000 psi, we can suit the material to the job and the customer’s cost restraints. We are continually researching and experimenting with new alloys and manufacturing processes – some with all around better strength and fatigue properties.” Smith: “Once the design work is done and material has been selected, what’s next?” “Next comes the actual process of manufacturing. It goes without saying that all high strength bolts must have rolled rather than cut threads, and that the threads must be rolled after heat-treatment. But there is more to it. The old saying to the effect of, “If you are doing something in a particular way because that’s the way it has always been done, the chances are that you are doing it wrong,” holds true in fastener technology. Technology advances, and we have to advance with it. All of the manufacturing processes should be subject to continuous experimentation and development. As an example, with some alloys, cold This spring was wound from un-shaved material. It failed on the seam line. 5 stage “Cold Header” used in the production of ARP bolts FASTENER TECH
16 heading produces a better product than hot heading, and vice versa. The number and force of the blows of the cold heading machine can make a significant difference in the quality of the end product. Excessive numbers of blows can lead to voids in the bolt head. ARP, in fact, holds significant patents on cold heading procedures for the higher nickel and cobalt based alloys. In a typical aerospace manufacturing process, these alloys are hot headed from bars, reduced in diameter from 48 to 50% by cold drawing, resulting in a hardness of about Rockwell C46 which is too hard for cold heading. So, the blanks are locally induction heated in a very narrow temperature envelope and hot headed. If care is not taken the process can reduce the hardness of the bolt head and the area immediately under it as much as 3 to 5 points on the Rockwell C scale. Subsequent heat-treatment does not restore this partially annealed area to full hardness and strength. Therefore, the final result can be a relatively soft headed bolt. This process is not preferred by ARP. Our patented process begins with a softer wire that can be cold forged. The process work hardens the head and the under head area to the desired hardness. We then power extrude the front end to achieve the reduction and hardness in the shank resulting in a bolt with even strength and hardness from end to end. The same is true of thread rolling. Temperature and die speed must be controlled and changed for different alloys. Many bolt manufacturers who meet the Aerospace Specifications don’t come close to meeting our standards. We consistently go beyond standard aerospace specs. Our concern with the manufacturing processes extends to the details of heat-treating, shot-peening, fillet rolling and grinding – down to the frequency of dressing the grinding wheels. In the arena where aerospace standards are a starting point and random failures are unacceptable, I feel ARP stands alone as a primary engineering and manufacturing source for specialty and custom fasteners for use in motorsports. It is important to realize that simply quoting an AMS (Aerospace Material Specification) number without strength and percentage of elongation numbers is meaningless. Statements that the use of a particular material will, in itself, result in extreme strength and resistance to fatigue can be misleading. In the world of high strength alloys, whether they are used for bolts or for landing gears, the manufacturing processes are at least as important as the material specification. Some in our industry claim to inspect materials at the “molecular” level. In metallurgical terms, molecules are not necessarily part of the vocabulary. Our engineers tell us that talking about molecules is misleading. When reference is made to metal, it is typically in terms of atom structures. We routinely check metallurgical features microscopically. By the way, the same is true for claims of manufacturing to “zero tolerance.” “Our engineers tell us that this is technically unrealistic.” FASTENER TECH
17 Smith: “How does the actual process work at ARP?” “For each new design, we produce a number of prototype parts using different design aspects and sometimes different methods. We inspect and test after each process, choose the best design and method of manufacture, and then freeze the design and write the manufacturing specification.” Smith: “You have mentioned the importance of fatigue resistance. Is there a difference in the procedures for strength and fatigue testing between aerospace and the specialty racing industry?” “Yes. While the ultimate tensile strength testing is the same, fatigue testing is different. Aerospace fasteners are fatigue tested to the relevant specification of fluctuating tension load and number of cycles typically 130,000 cycles with the high tension load at 50% of the UTS and the low load at 10% of the high load. If all of the test samples last 85,000 cycles (per AMS 5842-D), the lot is accepted. Even though racing fasteners are not continuously subjected to their maximum design load, at 18,000 rpm, 100,000 cycles takes just 5 minutes, thirty-four seconds. Except for drag racing, measured in seconds, no race lasts just 5 minutes. Therefore we consider this Aerospace Standard to be inadequate. At ARP, we fatigue test to elevated loads (10% above aerospace requirements) and to a minimum cycle life that exceeds 350,000 cycles. The majority of samples are routinely tested to one million cycles. During material development...and in the case of extremely critical new designs, we test to destruction. Thread rolling is the last mechanical operation in our manufacturing process. For each production run the thread rolling machine is shut down after a few parts. These parts are inspected for dimensional accuracy and thread quality, and are physically tested for both strength and fatigue before the run is continued. Random samples are inspected and tested throughout the run. Extremely critical components are individually inspected for dimensional integrity.” Smith: “What about out-sourcing?” “Economics often dictate that many processes in the manufacture of aerospace fasteners are farmed out. In the early days, ARP began as an out-source thread rolling shop. Over the years, however, we have found, through experience, that the only way to maintain the quality we require is to keep everything in-house. From heading through machining, grinding, heat-treat, thread rolling, and shot-peening to black oxide treatment we perform every operation in house on our own equipment with our own employees.” Smith: “Gary, One of the things that I am hearing is that every aspect of the manufacture of racing engine fasteners is more expensive than that of similar aerospace items.” “True, but the bottom line is that we have to look at the cost aspect of the very best fastener versus the cost aspect of a blown engine and a lost race. In the end, the manufacturing of fasteners for racing comes down to a matter of attitude; a refusal to accept published standards and procedures as the best that can be done and most of all a determination to learn and to make still better products.” Fatigue, tensile and hardness testing are key quality control checks. FASTENER TECH
18 There are literally hundreds of standards and specifications – for all types of applications, from bridges to rockets. None are as critical as those required for real-world motorsports applications. In an environment where lighter is faster there is clearly no room for redundant fasteners, like those found in military and aerospace applications. The mere nature of Motorsports requires designers to produce fasteners that are light; yet tough, fatigue-resistant and reliable beyond other acknowledged application standards. The design and production of fasteners, exclusively for racing, clearly involves many complex factors. Some are so unique and complex that no standards or design criteria exist. This means that everyone at ARP is entirely dedicated to the development and analysis of appropriate bolt designs exclusively for special applications. Our designs take into account the special loads that must be carried, the material selection, the manufacturing processes and the methods of installation required to deliver ARP quality and reliability. It is hoped that by providing an overview of the engineering, design and production techniques ARP applies daily, you – as the end user – will be better equipped to evaluate your initial fastener requirements, effectiveness and performance. Design Procedures for Automotive Bolts Presented by Dr. Kenneth Foster, PhD The design of automotive bolts is a complex process, involving a multitude of factors. These include the determination of operating loads and the establishment of geometric configuration. The process for connecting rod bolts is described in the following paragraphs as an example. The first step in the process of designing a connecting rod bolt is to determine the load that it must carry. This is accomplished by calculating the dynamic force caused by the oscillating piston and connecting rod. This force is determined from the classical concept that force equals mass times acceleration. The mass includes the mass of the piston plus a portion of the mass of the rod. This mass undergoes oscillating motion as the crankshaft rotates. The resulting acceleration, which is at its maximum value when the piston is at top dead center and bottom dead center, is proportional to the stroke and the square of the engine speed. The oscillating force is sometimes called the reciprocating weight. Its numerical value is proportional to: It is seen that the design load, the reciprocating weight, depends on the square of the RPM speed. This means that if the speed is doubled, for example, the design load is increased by a factor of 4. This relationship is shown graphically below for one particular rod and piston. Motorsports Fastener Engineering for the Non-engineer FASTENER TECH
19 A typical value for this reciprocating weight is in the vicinity of 20,000 lbs. For purposes of bolt design, a “rule of thumb” is to size the bolts and select the material for this application such that each of the 2 rod bolts has a strength of approximately 20,000 lbs. (corresponding to the total reciprocating weight). This essentially builds in a nominal safety factor of 2. The stress is calculated according to the following formula: so that the root diameter of the thread can be calculated from the formula: This formula shows that the thread size can be smaller if a stronger material is used. Or, for a given thread size, a stronger material will permit a greater reciprocating weight. The graph (see page 20) shows the relationship between thread size and material strength. It must be realized that the direct reciprocating load is not the only source of stresses in bolts. A secondary effect arises because of the flexibility of the journal end of the connecting rod. The reciprocating load causes bending deformation of the bolted joint (yes, even steel deforms under load). This deformation causes bending stresses in the bolt as well as in the rod itself. These bending stresses fluctuate from zero to their maximum level during each revolution of the crankshaft. The next step is to establish the details of the geometric configuration. Here the major consideration is fatigue, the fracture that could occur due to frequent repetition of high stresses, such as the bending stresses described above. Several factors “H” beam-deformed. Total translation contours. For loading in tension due to acceleration forces at 8000 RPM Motorsports Fastener Engineering for the Non-engineer FASTENER TECH
20 must be considered in preventing fatigue; attention to design details is essential. Fatigue failure is frequently caused by localized stress risers, such as sharp corners. In bolts, this would correspond to the notch effect associated with the thread form. It is well known that the maximum stress in an engaged bolt occurs in the last engaged thread. By removing the remaining, non-engaged threads, the local notch effect can be reduced. This leads to the standard configuration used in most ARP rod bolts: a reduced diameter shank and full engagement for the remaining threads. Providing a local fillet radius at the location of the maximum stress further reduces the local notch effect. Thus this configuration represents the optimum with respect to fatigue strength. The reduced diameter shank is helpful in another sense. It reduces the bending stiffness of the bolt. Therefore, when the bolt bends due to deformation of the connecting rod, the bending stresses are reduced below what they would otherwise be. This further increases the fatigue resistance of the bolt. A typical bolt configuration is shown below. Once the bolt configuration has been established, the manufacturing process comes into play. This involves many facets, which are discussed in detail elsewhere. Here, however, one process is of primary interest. With respect to bolt fatigue strength, thread rolling is a major consideration. Threads are rolled after heat treating. This process, which deforms the metal, produces a beneficial compressive stress in the root of the thread. It is beneficial because it counteracts the fluctuating tensile stresses that can cause fatigue cracking. If heat-treatment were to occur after rolling, the compressive stresses would be eliminated. This would therefore reduce the fatigue resistance of the bolt. An additional factor must be taken into account in defining the bolt configuration: the length of engaged thread. If too few threads are engaged, the threads will shear at loads that are lower than the strength of the bolt. As a practical matter, the thread length is always selected so that the thread shear strength is significantly greater than the bolt tension strength. This problem is especially important in bolts used in aluminum rods because of the fact that the shear strength of aluminum is much lower than the shear strength of steel. Motorsports Fastener Engineering for the Non-engineer FASTENER TECH
21 Finally, although not a design parameter, the subject of bolt installation clamp load must be addressed. It is a fundamental engineering concept that the force in a bolt in an ideal preloaded joint will remain equal to the clamp load until the externally applied force exceeds the clamp load. Then the force in the bolt will be equal to the external force. This means that fluctuating external forces will not cause fluctuating forces in a preloaded bolt as long as the clamp load exceeds the external force. The result is that fatigue failure will not occur. In a non-ideal joint, such as in a connecting rod, the bolt will feel fluctuating stresses due to fluctuating rod distortions. These are additive to the clamp load, so that fatigue could result. In connecting rods, precise clamp loads are required because if they are too low, the external forces (the reciprocating weights) will exceed the clamp load, thus causing fatigue. If they are too high, they provide a high mean stress that combines with the fluctuating stresses due to rod distortion. Again, fatigue is promoted. The objective, then, is to preload a bolt so that it just exceeds the external load, and no higher. To sum up: both insufficient and excessive clamp loads can lead to fatigue failures. Appropriate clamp loads are specified for each ARP bolt. These clamp loads can be attained in a connecting rod by applying proper torque using a torque wrench or by measuring the amount of stretch in the bolt using a stretch gauge (it is known that a bolt stretches in proportion to the tension in it). The torque method is sometimes inaccurate because of the uncertainty in the coefficient of friction at the interface between the bolt and the rod. This inaccuracy can be minimized by using the lubricant supplied by ARP. Other factors, equally as important as design, include material selection, verification testing, processing, and quality control. These aspects of bolt manufacturing are discussed elsewhere in this document. The foregoing discussion concentrated on the design of bolts. The same considerations apply in the design of studs. Motorsports Fastener Engineering for the Non-engineer FASTENER TECH
22 Recognizing Common Failures There are six types of metallurgical failures that affect fasteners. Each type has unique identifying physical characteristics. The following chart is designed to be used like a spark plug reading chart to help analyze fastener failures. While few of us have access to sophisticated analysis equipment, a standard Bausch and Lomb three lens magnifying glass will generally show 98% of what we want to see. Several of the photos below have been taken utilizing a Scanning Electron Microscope (SEM) and are presented to simply illustrate typical grain configurations after failure. 1. Typical Tensile Overload In a tensile overload failure the bolt will stretch and “neck down” prior to rupture. One of the fracture faces will form a cup and the other a cone. This type of failure indicates that either the bolt was inadequate for the installation or it was preloaded beyond the material’s yield point. 2. Torsional Shear (twisting) Fasteners are not normally subjected to torsional stress. This sort of failure is usually seen in drive shafts, input shafts and output shafts. However we have seen torsional shear failure when galling takes place between the male and female threads (always due to using the wrong lubricant or no lubricant) or when the male fastener is misaligned with the female thread. The direction of failure is obvious and, in most cases, failure occurs on disassembly. 3. Impact Shear Fracture from impact shear is similar in appearance to torsional shear failure with flat failure faces and obvious directional traces. Failures due to impact shear occur in bolts loaded in single shear, like flywheel and ring gear bolts. Usually the failed bolts were called upon to locate the device as well as to clamp it and, almost always, the bolts were insufficiently preloaded on installation. Fasteners are designed to clamp parts together, not to locate them. Location is the function of dowels. Another area where impact failures are common is in connecting rod bolts, when a catastrophic failure, elsewhere in the engine (debris from failing camshaft or crankshaft) impacts the connecting rod. 2. 3. 1. FASTENER TECH
23 Recognizing Common Failures 4. Cyclic fatigue failure originated by hydrogen embrittlement. L-19, H-11, 300M, Aeromet 100 and other similar high strength “quench and temper” steel alloys, popular in drag racing, are particularly susceptible to “hydrogen embrittlement.” Extreme care must be exercised when handling these materials, and kept well oiled at all times to prevent hydrogen gas and moisture from accumulating and attacking the metal. This type of failure is easily mistaken with Stress Corrosion. The spot on the first photo is the origin of the crack and the original stress riser. The second photo is a SEM photo at 30X magnification. 5. Cyclic fatigue cracks propagated from a rust pit (stress corrosion) Again, L-19, H-11, 300M and Aeromet 100, are particularly susceptible to stress corrosion, while 8740 and ARP2000 alloys are less susceptible to stress corrosion. These materials must be kept well oiled at all times and never exposed to moisture including sweat. The photos illustrate such a failure. The first picture is a digital photo with an arrow pointing to the double origin of the fatigue cracks. The second photograph at 30X magnification shows a third arrow pointing to the juncture of the cracks propagating from the rust pits. Inconel 718, ARP 3.5 and Custom Age 625+ are immune to both hydrogen embrittlement and stress corrosion. 6. Cyclic fatigue cracks initiated by improper installation clamp load Many connecting rod bolt failures are caused by insufficient clamp load. When a fastener is insufficiently preloaded during installation the dynamic load may exceed the clamping load resulting in cyclic tensile stress and eventual failure. The first picture is a digital photo of such a failure with the bolt still in the rod. The white arrows indicate the location of a cut made to free the bolt and the black arrow shows the origin of the fatigue crack. In the second picture – an SEM photo at 30X magnification clearly shows (1). The origin of the failure and the telltale “thumbprint” or “beach mark” (2). Tracks of the outwardly propagating fatigue cracks and (3). The point where the bolt (unable to carry any further load) breaks-away. 6. 5. 4. FASTENER TECH
24 The following material is intended to provide a brief overview of the metallurgical considerations that, daily, influence the design and production of the most reliable fasteners in motorsports. It is hoped that a simple understanding of the knowledge and commitment required to produce this reliability will make your future fastener decisions much, much easier. By Russell Sherman, PE 1. What is grain size and how important is it? Metals freeze from the liquid state during melting from many origins and each one of these origins grows until it bumps into another during freezing. Each of these is a grain and in castings, they are fairly large. Grains can be refined (made smaller); by first cold working and then by recrystallizing at high temperature. Alloy steels, like chrome moly, do not need any cold work; to do this – reheat treatment will refine the grain size. But austenitic steels and aluminum require cold work first. Grain size is very important for mechanical properties. High temperature creep properties are enhanced by large grains but good toughness and fatigue require fine grain size – the finer the better. All ARP bolts and studs are fine grain – usually ASTM 8 or finer. With 10 being the finest. 2. How do you get toughness vs. brittleness? With steels, as the strength goes up, the toughness decreases. At too high a strength, the metal tends to be brittle. And threads accentuate the brittleness. A tool steel which can be heat-treated to 350,000 psi, would be a disaster as a bolt because of the threads. 3. Define Rockwell as we use it. Why do we use the C scale? A man named Rockwell developed a means of measuring hardness of metals which was superior to other methods. A Rockwell hardness tester measures the depth of penetration into the metal when a load is applied. For hard materials, a diamond penetrator is used. For soft material, small balls are used – 1/16˝ or 1/8˝ diameter-and the machine measures the depth. We use the C scale for the 120,000 psi strength level and above. The C scale uses the greatest load – 150 Kg. The A scale uses only a 60 Kg. load but can be correlated with C. It is necessary to use the A scale for thin sheets because using the 150 Kg load would cause the diamond to penetrate almost all the way through. ARP engineers use “Scanning Electron Microscopic” inspection capable of detecting all elements in the periodic table with atomic numbers greater than 5 – permitting the acquisition of high resolution imaging. Metallurgy for the Non-Engineer FASTENER TECH
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