Racing Fasteners - The Ins & Outs Of Nuts & Bolts

These are manufactured from a carbon alloy steel and are also plated with zinc, usually of a yellow or gold hue, although some are silver colored. They have been heat treated to a higher level and the bolt is much harder. This type of bolt has six raised lines on the head. If you have an application where a good deal of strength is required, this is the grade of bolt you need and should use in structural applications, shock mounts, and suspension pickup points. Grade 8 bolts are safe to use on basically every application on the racecar with the exception of wheel studs and highly loaded engine fasteners such as rod bolts, main bearing cap bolts or flywheel bolts.

Racecars, of course, are often taken apart and reassembled, and this is even harder on the nuts and bolts on cars raced on dirt due to the grit that will find its way into every nook and cranny. Nuts and bolts do not last forever, so you need to think of replacing the hardware on your car on a regular schedule. It is cheap insurance.

If you are racing a Street Stock, you should be able to use Grade 5 and Grade 8 nuts and bolts and never have any serious issues. As you start to modify the engine from an external perspective, an area that deserves some attention is the exhaust system, specifically header flange hardware. The exhaust on racecars goes through some extreme changes in temperature. These changes cause sealing issues as the headers, cylinder head and header bolts expand and contract as the engine goes through heat cycles. This can and does lead to exhaust leaks and the hardware gets the blame. The last place you need any problems is in the exhaust system, especially if it is completely preventable. It is not an issue with the hardware loosening up, as it is usually traceable to gaskets being unable to seal after multiple expansion and contraction cycles. This is especially an issue with aluminum heads. The biggest problem here is with the inability to adequately tighten the bolts to the correct torque levels due to header tube interference. This may mean some different hardware with smaller heads to help generate adequate tool clearances so you can generate the correct torque levels. ARP makes some very good header bolts that will work very well for almost any racing application.

One of the biggest problems I observe while in the pits is watching people over-torque bolts and nuts. Many people think that if a little force applied to a wrench is a good thing, then more must be better, but nothing could be farther from the truth. Get a couple of quality torque wrenches and use them, and get some automotive specification books and look up the torque value for the nuts and bolts you are tightening. If you are using aftermarket racing parts they will have torque values for the fasteners supplied by the makers, so look them up and use them. Just tightening a bolt up to a random value is not the best use of the tools we have at our disposal.

You can find the torque values for a particular fastener on many different Web sites, such as www.zerofast.com/torque.htm. This site will give you the torque values for a variety of fasteners. Over-torquing the bolts and/or the nuts is not a good thing. It can lead to nuts and bolts yielding and that leads to failure. The point is that the information is out there and all you have to do is just ask the question. If you do not have Internet access, most public libraries have free access.

The cost of bolts, nuts and quality washers is a fractional cost of the car, and if poorly matched to a specific task can cause catastrophic damage. The cost of such a failure can make the cost of the nuts and bolts insignificant in comparison to the damaged caused. Don't try to save a buck on a bolt. Look for saving opportunities in other areas.

The author can be reached at Vahok.Hill@cox.net.

The torque wrench is a tool that every racer needs to have. To properly use a bolt you need to torque it to the proper value to get the full advantage of the strength the bolt has to offer. Too much torque can yield the bolt and over time it may fail. It is a good idea to have a variety of torque wrenches. This way you will have the correct tool to torque the fasteners on your car to the correct values. The cost is not that great and it is good insurance. Photo by John Hill