Also, a good rule of thumb for most situations is to pick a clutch that will hold your engine's horsepower, plus 10 percent. If you're packing 500 hp, then a clutch rated for 550 hp will be a good match for you.
Let's take a look at two of those application categories:
OEM replacement and daily driver applications fit very well into this category. It's a little hard to put horsepower limits on street clutch kits, as their ratings depend on several things, but we would ballpark this category at around 350-400 hp. Most stock pressure, organic clutch kits will hold their own for quite a while. Usually, the breaking point is when you start adding a few performance mods or start getting aggressive with sticky tires. You can expect a light to moderate pedal pressure with most of these kits, along with no chatter and a gradual engagement. If you need something with a little more room, the RAM HDX series clutch kits are great for lightly modified vehicles and are generally rated to about 450 hp. They also feature 100- percent-organic discs, but the pedal pressure may be slightly increased.
This category can cover a lot of ground, as there are dedicated race cars that run the gamut from stock engines to the ridiculously modified. For the scope of this article, we'll propose a horsepower range somewhere between 450-1,000 hp. Broad range, right? There are lots of viable solutions for this type of application as well.
It gets trickier to choose a street/strip-style clutch because when the kind of performance levels that are in this category are reached, you start to lose sight of, or the need to have, perfect street manners and clutch engagement. If you insist on a very light pedal pressure or no chance of chatter at all, then a thorough evaluation of vehicle weight, rearend ratios, and more, has to be completed to see if that can be achieved. If none of this is a concern, then it's best to aim for the horsepower ôplus 10 percentö rule, and make a decision based on flywheel/transmission specs and cost.
There are many different high-quality clutch manufacturers that are available to us including RAM, McLeod, Spec, Fidanza, Hays, and Centerforce. As an example, with the McLeod brand, you can pair one of the company's heavier duty long-style or diaphragm pressure plates with one of its 500-series discs and be covered up to more than 500 hp. Pairing that same pressure plate with a 600-series disc will extend that rating up to 600 hp.
RAM's Powergrip series pairs a long or diaphragm pressure plate with an organic/sintered iron disc to achieve a 550hp rating. Typically, this would be an aggressive combination, but RAM uses a lighter static pressure on the pressure plate, so pedal pressure is very light. Along the same lines, the RAM Powergrip HD series uses the same pressure plate but uses a sintered iron disc to allow up to 650 hp to make it through. This author has personally used this clutch on a 7.50-second, 1?8-mile-class Fox Mustang and it was very streetable without any chatter. However, the car also sported 4.30 rearend gears.
When you start dealing with engines with more than 650 hp and you want to stay on the streetable side of things, then the twin-disc clutches are the way to go. Most of the companies mentioned previously now offer twin-disc clutches. The McLeod RST, for example, is rated for 800 hp and sports a diaphragm pressure plate with twin organic discs. It also offers a very light pedal pressure and very good engagement/disengagement manners. The RXT has dual-friction discs and is rated for 1,000 hp.
Most twin-disc setups utilize a specific flywheel as part of the clutch kit--something to consider when you see the higher prices of the twin-disc setups. These specific flywheels are often much smaller in diameter than stock, and help reduce rotating mass. You can even get some of these combinations with an aluminum flywheel.