When you pay good money for horse-power, you want that power to go to the wheels as planned. Cars with manual transmission have a virtual Twilight Zone of variables, so to speak, that can rob you of those hard-earned horses. A car's flywheel, clutch, pressure plate, and, yes, even the throwout bearing, can be one of many complex problems. As the mechanism for transferring the engine's revolutions to the transmission, there are always opportunities for loss. That loss can happen when you are in a restart or other critical times on the track. There's never any insurance against blowing a restart, but you can try to make sure your equipment is not the cause.
With so many different types of cars racing under different rules, the amount of information on these components would quickly fill the pages of this magazine. Taking the time to ensure your clutch assembly is put together right and utilizes the right components can be complicated, so you need to know about clutches and their respective components. Remember, there is no "off the shelf" system for your application. Also, because knowledge is power, the best tip we know is to call the tech line of a supplier to get the perfect application for your needs. It helps to have a little background before you make that call.
General Tips
* The ring gear flywheel size determines your clutch size, 1011/42 or 11 inches. The flywheel has to fit within the bolt circle of the crank and match up to the pressure plate. It's only one part of a system. If you remember that, you'll make fewer trips back to the parts store for the right pieces.
* Should you use a steel or aluminum flywheel? Generally, when you run a higher rpm (6,500 and up), you'll need an aluminum flywheel. Less reciprocating weight and less spinning mass equals higher recovery rate, or the time it takes to get both the flywheel and your tranny up to matching speeds. For comparison, here are some weights to remember: stock Chevy flywheel-25 pounds; steel aftermarket, SFI approved-25-40 pounds; aluminum aftermarket-15 pounds.
* If you're running a Street Stock or some form of heavy car, you'll need more torque to move its weight. A steel flywheel can help. The same holds true for classes with engines that don't turn the higher rpm (less than 6,500). If your class has a cam rule limiting your engine to a 440-460 lift cam, you can use the steel flywheel.
* On the other end of the scale, cheater pressure plates-made especially for circle track-weigh only 12 pounds, or roughly half of a normal pressure plate's weight. They're made for rules that stipulate use of a stock-appearing pressure plate. Couple this with a 15-pound flywheel and you shave off quite a bit of reciprocating weight. These components are made for higher-revving motors, so more of what you've paid for reaches the rear wheels.
* If you're looking for a standard configuration aluminum flywheel that can hold up to the rigors of racing, there are some available that use friction materials consisting of bronze and iron. The different material allows for better contact between the clutch disc and flywheel while the aluminum saves weight. Those contact areas can be replaced when needed.
* When changing a clutch or pressure plate, always change the throwout bearing. It's cheap insurance. Throwout bearings are responsible for 85 percent of clutch wear.
* Throwout bearings require an air gap between the bearings and the pressure plate. The recommended size is usually 31/416-11/44 inch, but the gap will depend on the style of clutch. If it's not spaced properly, it will hang up. We all know what can happen to an engine when a shift is missed. This clearance is even more critical on the longer styles. The wrong gap will wear out the bearing faster and take other parts with it.