KJ Jones
December 19, 2013
Photos By: K.J. Jones

Horse Sense: Throughout the '70s and well into the '00s and beyond, Quarter Master has long been recognized for clutch systems designed for circle-track racing. However, despite making its mark in roundy-round competition, a little known fact about the company is that it actually started out as drag-race chassis manufacturer; Quarter Master (for quarter-mile... get it?). It's all in the name!

Working with bad-dude Mustangs is our daily mission here. Be it a feature story on a hot-looking Pony, or a technical report on an innovative new part, bringing you wall-to-wall coverage about the latest and greatest is what we do.

While Mustang LXs and GTs are our typical beat, there are occasions when our spotlight shines on Shelby GT500s. These factory-supercharged, Four-Valve beasts respond well to basic bolt-ons and tuning.

Of course, GT500s are plenty awesome in bone-stock form, so the aforementioned upgrades typically are made based on owners' desire to improve their Ponies, as opposed to there being a specific need for different hardware. However, with this being said, the clutch is one component that actually needs addressing when you decide to take a Shelby's power and torque into the 700-1,000hp stratosphere, which seems the norm for modded Shelbys.

As with any stick-shifted 'Stang, the clutch makes all the difference in ensuring every bit of the engine's performance is transmitted from the engine to the rear wheels. Interestingly, Ford's latest higher-output Mustangs rely on factory-installed, Sachs twin-disc clutch units that are great at stock power levels, but can fold like a weak hand in the face of big steam. Enter Quarter Master Racing Clutches and Driveline Components (www.quartermasterusa.com) with a new twin-disc clutch option for stout street Shelbys.

The company's Optimum-SR 10.4 Two-Disc System (PN 226050190-R; $2,312.50) is lightweight clutch-and-flywheel hardware for '11-'13 GT500s that supports massive power and grunt, without sacrificing easy pedal operation or street driveability. With several basic mods already handled, Saoud Alahmad's '12 Shelby is beyond-stock stout, and a good candidate for installing and evaluating Quarter Master's first Mustang performance unit.

We followed along as Cody Volkenant of Addiction Motorsports bolted the Optimum-SR unit in Saoud's supercharged Pony. While the clutch kit and the hydraulic clutch-release bearing (PN 713402) and adapter (PN 730023) we installed can't be categorized as low-buck, they're quality choices for high-end Shelby 'Stangs with extra oats. Installing this setup is best left for the experts to handle, as exhaust and drivetrain pieces must be removed, and extremely detailed measurements are necessary for doing it properly.

Addiction Motorsports technician Cody Volkenant preps Quarter Master Racing Clutches’ all-new twin-disc clutch system for ’11-’14 Shelby GT500 ‘Stangs, while Saoud Alahmad’s ’12 Shelby waits patiently on the hoist to receive it.
Saoud’s ’12 is perfect fodder for a high-performance clutch system, as it’s equipped with such bolt-ons as long-tube headers, a smaller supercharger pulley, CAI, Ford Racing Performance Parts throttle body, and an Eddie Rios/SCT tune. The combination puts 580 hp at the feet with 680 lb-ft of torque—a blower upgrade (and fuel system) away from making the next-level power that is common for modified Shelbys.
Saoud’s ’12 is perfect fodder for a high-performance clutch system, as it’s equipped with such bolt-ons as long-tube headers, a smaller supercharger pulley, CAI, Ford Racing Performance Parts throttle body, and an Eddie Rios/SCT tune. The combination puts 580 hp at the feet with 680 lb-ft of torque—a blower upgrade (and fuel system) away from making the next-level power that is common for modified Shelbys.
Made primarily of billet aluminum, the Optimum-SR 10.4-inch clutch package truly is a beautiful piece. We had to give you this look at how nice it is before it’s hidden by the bellhousing.
After disconnecting the negative battery cable and securing the ‘Stang on a drive-on hoist, Cody removes the exhaust (long-tube headers must come off) and drivetrain ancillaries, and then pulls the Tremec T-6060 six-speed transmission away from the engine.
Here’s a side-by-side comparative look at the OEM twin-disc clutch package (left) and our Quarter Master unit. The new setup weights in at approximately 42 pounds, which is substantially lighter (about 18 pounds) than the stock Sachs twin.
Components in a twin-disc clutch system are stacked in the following order (from bottom to top): flywheel, disc, floater plate, disc, floater plate, pressure plate. Unlike other dual-disc systems, Quarter Master incorporates tall posts into the flywheel, into which the pressure plate is secured. The posts also serve as containment for the entire package.
When disassembling the clutch package, Cody indexes the correct position for the cover ring by marking common points on the ring and a flywheel stanchion. Doing this ensures the cover’s mounting straps are properly aligned.
The system’s billet floater ring contains holes that are designed to help dissipate heat and cool the clutch (by circulating air into the assembly), similar to the way ventilated brake rotors work.
Clutch discs are made from a high-metallic, proprietary, glass/polymer-based, organic friction material. Other systems rely on ceramic disc material.
The flywheel is installed first. Cody uses red Loctite on the ARP 7⁄16-inch bolts and torques the fasteners with 85 lb-ft.
While a pilot tool is a key element of any clutch install, using a good one is critical for dual-disc installations. Addiction Motorsports relies on a decommissioned T-56 input shaft (26-spline) for keeping things in line during twin-disc installs.
After installing the bottom disc (and making sure the flange side of the hub is pointed outward, toward the transmission), Cody mounts the floater plate to the assembly. Again, red Loctite is used and the fasteners are secured with 25 lb-ft of torque.
The pressure plate is the Quarter Master twin-disc system’s final component. Cody installs the plate so that its copper-colored cover is aligned with the flywheel stands, and then secures the cover’s fasteners with 30 lb-ft of torque.