GM's LS-series small-block engines pack a powerful punch in their various forms, from the base Vette's LS3 to the king LS9. Better still, increasing horsepower and torque in any LS platform is almost too easy. The market offers dozens of cylinder heads, camshafts, intake manifolds, exhaust mods, fortified internals, nitrous oxide, and several types of supercharger and turbocharger systems. As a result, a street-driven 1,000-rwhp Vette is no longer a topic for science-fiction movies. The unfortunate reality is that drivetrain durability under such extreme conditions will unavoidably suffer. Thankfully, racing technology has trickled down to the streets, and the latest dual-disc clutch systems can handle almost anything an LS engine is capable of throwing at it.
The dual-disc clutch was born from the high demands in certain racing arenas, particularly circle-track competition. By spreading the clamping force over two clutch discs, these units provide superior holding power without significantly increasing pedal feel. Dual-disc clutch technology spread to other racing disciplines and eventually found its way to the street crowd, albeit with a few mods to make these setups friendlier in everyday use. (While chatter plagued some early aftermarket dual-disc clutches, most companies have since modified their designs to provide a silk-smooth feel.)
The trickle-down effect continued, and last year the ZR1 Corvette brought dual-disc clutch technology to the GM parts bin. Realizing that none of their existing single-disc units could properly harness the LS9's 604 lb-ft of torque, GM engineers were forced to get creative. Their solution came in the form of a dual-disc system with twin 260mm discs. (To put that into perspective, the C6 Z06 utilizes a single 290mm disc to back the naturally aspirated LS7.)
We've watched several high-profile ZR1s pound out 10-second passes on the dragstrip and lay down scorching runs on the chassis dyno without a hint of clutch problems. That's quite an accomplishment considering the LS9's TVS-style supercharger, which is known for its big, aggressive torque curve. (Rumor has it that GM engineers have actually tested this clutch up to a staggering 800 lb-ft.) We should note that the ZR1 isn't the only OEM vehicle to offer a twin-disc clutch setup: Its archenemy, the Viper, has one behind its V-10 powerplant, and the V-8 Challenger does as well.
Thanks to the aftermarket's ingenuity, ZR1 technology is no longer limited to the top-of-the-line Vette. We recently road-tripped to Redline Motorsports in Schenectady, New York, to follow along as the shop converted a base C6 Vette from a single-disc clutch combo to a ZR1 dual-disc setup. The conversion is relatively easy, thanks to a combination of parts from GM and Lingenfelter.
Redline's list of components for this swap show a ZR1 slave cylinder (PN 24237569, $237.34 from local dealer), a ZR1 clutch (PN 24237568, $624.54), and a Lingenfelter Performance Engineering flywheel (PN L360010105, $824.95 from Redline Motorsports). The guys at Redline did suggest that a pilot bearing might be required for Corvettes with high mileage or hard use.
Our test subject was an '09 Corvette whose LS3 had been warmed over with a custom Redline Motorsports camshaft, CNC-ported factory heads, American Racing Headers long-tubes and exhaust, a cold-air kit, and a custom Redline ECM calibration. In this trim, the Vette spun the shop's chassis dyno to an impressive 506 rwhp and 455 rwtq. The stock clutch had been holding up fine to the torque output, but with a new Edelbrock E-Force TVS supercharger on the way, the car's owner and the Redline crew felt an upgrade was in order. Shop owner Howard Tanner estimated that rear-wheel power and torque would swell past the 600 mark with a modest 5-7 psi of boost. "This C6 definitely needs an upgraded clutch with the forthcoming Edelbrock blower," he said.