For structural or chassis mounting, use Grade 8 or better bolts. These have six lines stam
Grade 5 bolts are manufactured from a medium grade of carbon steel. They are also zinc plated and heat treated to a tempered state. This is the minimum grade that should be used in race car applications. Grade 5 bolts are easily identified by the three raised lines on the head of the bolt. As the Grade 2 bolts have no markings on the head, the addition of three lines on the head of the Grade 5 bolt (2+3=5) make it easily identifiable.
Good selections of Grade 5 bolts can be found in the hardware sections of local home improvement stores and better hardware stores. Most auto part stores carry them as well. There is also a plethora of hardware sources on the Internet. The only problem with the Internet sources is that you have to know exactly what you want. It is more difficult to browse the hardware section and impossible to touch the product on the Internet. Grade 5 bolts are reasonably priced and have sufficient strength for most of the non-engine-related and non-structural functions on a race car.
Grade 8 bolts are manufactured from a carbon alloy steel and are also plated with zinc, but they usually have a yellow or gold hue (although some are silver colored). They have been heat treated to a higher level and are much harder. There are six lines on the head of a Grade 8 bolt. If you have an application that requires a good deal of strength, this is the grade of bolt you should use.
A bird's eye view into the ARP manufacturing facility. It takes specialized processes, mac
There are many makers of bolts around the world, and some of these manufacturers are dedicated to making nuts, bolts, and studs exclusively for the racing industry. As racers, we are lucky to have people who make specialty fasteners for our industry. The bolts, studs, and nuts used on racing engines alone are unique and require a good deal of research and development to provide optimum performance in the intended application.
The infrastructure requirements needed to make special hardware are way beyond those of even the most resource-rich professional racing teams. It takes very specialized equipment and highly controlled processes, not to mention chemical processes and special material labs, to ensure quality and consistency from lot to lot. ARP makes a variety of very specialized fasteners for the racing industry. Chris Raschke works for ARP and has some unique insights regarding the use of nuts and bolts on race cars.
"The act of installing and removing the head bolts on an engine during the disassembly process can place undue stress on the threaded hole and the block," says Raschke. As racers, we have a tendency to take our cars apart and reassemble them as part of the maintenance and tuning process. This activity can cause excessive wear and tear on vital parts of the car. On engine surfaces for example, we take a great deal of time and incur some very high costs to make sure mating surfaces are flat and free from imperfections. Then we take them apart frequently.
Header bolts have smaller heads to assist in installation. With headers, due to larger por
The installation and removal of head bolts can also create burrs around the threaded areas, impacting the flatness of the surface. If the block is aluminum, the opportunity for damage is even greater. This added stress can be eliminated by replacing the OE bolts and the accompanying special washers and nuts with studs. Not only does the use of studs in this application reduce the wear and tear on the block, but they also generate more even load distribution of the clamping forces required to prevent head gasket failures. And, as an added bonus, they hold the gasket in place during the assembly process.
What other areas of the race car should get a better grade of hardware than was supplied as part of the OE package? Raschke has some good insight regarding what the racer should be looking toward when replacing hardware. "Any area that is subject to high maintenance (this equates to frequent assembly and disassembly), for example, bolts on the rearend that hold the third member in place, should be replaced with a stud kit," Raschke says. "This will speed gear changes and help prevent excessive wear of the threads in the axle housing. It also promotes better gasket sealing."
We need to remember that these stock components were not designed for the high frequency of use expected of racers. In the stock application, they were designed to be installed once at the factory and then last multiple years prior to any disassembly. As racers, we may remove these bolts several times on a race day, or at the very least, several times a month. There are multiple locations on your race car where it makes good sense to utilize studs and nuts versus a bolt alone.