If you've ever had the misfortune of driving a modified Corvette with a terrible clutch, you know all too well how badly it can affect the entire driving experience. And we're not talking about a stock unit that's slipping—we're talking about a calf-straining beast that acts more like an on/off switch than a smoothly modulating unit.
Slowly leaving a parking lot? Here, let me chatter twice, bog, and then shut off on you. Trying to slip the clutch a bit at the track? Best I can do is full engagement right off the floor and an embarrassing 2.6-second 60-foot time. Yes, a bad clutch can ruin everything.
Do I sound bitter? Maybe, but I've had the displeasure of driving horrible clutches in a variety of cars for years. Some grabbed right off the floor, some waited until the very tippy top of the pedal travel, and some just did whatever they liked whenever they felt like it. Too grabby, too "slippy," too firm, too soft…it can be hard to find one that's just right, and considering that installation involves removing the entire driveline on a fifth- or sixth-generation Vette, it's important to make the right choice the first time.
So, when Quarter Master released its new single-disc Optimum-SR clutch package for the C5 (a dual-disc unit is also available), we had a decision to make: Stick with an old favorite, or try the new kid on the block?
On paper, the stats are impressive. Featuring billet construction, the Optimum-SR 10.4-inch single weighs 50 percent less than a factory LS6 clutch and can hold up to 700 hp and 500 lb-ft of torque. According to the company, the kit's lighter weight "creates reduced Moment of Inertia (MOI), allowing the engine to rev and de-rev quicker than a stock OE unit." A sprung hub and proprietary spring technology are said to allow for a higher clamp load while still offering excellent power modulation and release force.
Finally, the entire clutch is rebuildable, should it need service down the road, which can save you money in the long run. At $2,145, it's not the cheapest offering on the market, but, as is often the case with aftermarket performance parts, you get what you pay for in the clutch world.
Of course the real question is, how does it drive on the street? Our test car, a 445rwhp '03 Corvette Z06, rolled into the shop at AntiVenom in Seffner, Florida, running a thrice-replaced factory LS6 clutch. The pedal feel was smooth as silk, and engagement was good, but in the upper-rpm range (6,000-plus), the car would no longer shift into the next gear.
With the Quarter Master unit installed, our immediate thought was that something in the hydraulic system must be wrong. The pedal was so soft, so velvety, that we couldn't actually believe the clutch was engaging. A couple of tests proved everything was working correctly, and the pedal was in fact just that easy! It was like a stock clutch right off the assembly line: silky smooth, without any intense pedal effort.
Clutch in, drop it in gear, and we're off. Chatter? None. Bucking? None. Driveline noise? Nope. Quicker revs? Absolutely. High-rpm shifting problems? Gone! Smiles? All around. The Optimum-SR really did feel like a factory unit (much like a stock LS7, if you've driven one), but it allowed the engine to rev quicker and the clutch to engage faster. Even if you're a clutch cynic like me, this is one billet beauty that will keep you smiling.