Gear Bangers Part IV

Wayne Scraba

23 Jan 2020

Click Here to Begin Slideshow Over the last several issues, we’ve taken an in-depth look at the brand-spanking-new ST-246 clutch from the folks at Tilton. If you recall, this is an all new clutch configuration from Tilton that borrows technology from their serious racing clutch packages. Here, though, the idea was to build something you can use on the street and at the same time, harness an engine with modern levels of power. While the discs and pressure plate along with the general design have a lot to do with the clutch, you can’t forget the flywheel. Tilton spent a lot of time working out a steel flywheel that for all intents and purposes is as light as many aluminum jobs. It should be no secret a number of companies offer billet steel flywheels, but with the Tilton billet setup, the flywheel is CNC-machined from chrome moly steel. Unlike other clutches that rely on loose-fitting dowels or bolts to locate the clutch to the flywheel, Tilton utilizes a precision machine step on the flywheel to locate the clutch and provide optimal balance. A step measuring 0.100-inch tall is built into the flywheel. This step is for the clutch friction surface. You’ll note in the photos that all unnecessary material is removed from the flywheel. Obviously, the reason for this is to reduce overall flywheel weight. While Tilton could have machined the flywheel to be lighter, they engineered the mass of the flywheel to provide a good combination of performance and drivabilty. If the clutch/flywheel assembly is too light, drivability on the street suffers. Where many aftermarket flywheels are two-piece designs with separate ring gear assemblies, the Tilton flywheel is one-piece construction. Flywheels for conventional Chevys with two-piece rear main seals are only available in 153-tooth ring gear combinations. This means the flywheel, including the ring gear, measures 12-3/4 or so inches in diameter. In comparison, a 168-tooth flywheel for the same combination will typically measure approximately 14-1/4 inches in diameter. The only time this will become a big consideration for most engines is when the oil pan is an aftermarket job with a big kickout that mandates a large diameter ring gear. Otherwise, the small diameter ring gear setup will work. Keep in mind, too, that the smaller diameter flywheel plays a considerable role in reducing inertia. Recall that “if the weight in a rotating mass is moved closer to the center of the mass then the entire assembly can spin faster.” The lightweight small diameter flywheel allows the engine to spin up quicker. It’s that simple. Finally, Tilton notes that the ST-246 clutch and flywheel are balanced separately from each other, so there is no need to index the clutch to the flywheel. Something else we have to mention is the included hardware: Tilton packages a set of ARP flywheel bolts with the kit and also includes a set of 12-point 3/8-inch aircraft quality bolts and AN-washers to attach the pressure plate to the flywheel. FYI, the clutch to flywheel bolts must be torqued to 35 lb-feet while the flywheel to crank flange bolts must be tightened to 75 lb-feet. Locking compound should be used on the pressure plate bolts, while thread lube on the threads and under the head of the flywheel bolts is recommended. In the end, do these small diameter dual disc systems work? Absolutely. The small diameter dual disc clutch assemblies provide a pedal feel that is actually very light, and more in line with what you might find in a typical four-cylinder economy car. As you can see, Tilton has taken their decades of racing technology and applied it to the street-strip car. Not only is torque capacity increased, pedal pressure is reduced. It’s a win-win situation. And from a quality perspective, you’ll be blown away the moment you open the box. For a closer look, check out the accompanying slideshow.

Gear Bangers Part IV — Click Here to Begin Slideshow Over the last several issues, we’ve taken an in-depth look at the brand-spanking-new ST-246 clutch from the folks at Tilton. If you recall, this is an all new clutch configuration from Tilton that borrows technology from their serious racing clutch packages. Here, though, the idea was to build something you can use on the street and at the same time, harness an engine with modern levels of power. While the discs and pressure plate along with the general design have a lot to do with the clutch, you can’t forget the flywheel. Tilton spent a lot of time working out a steel flywheel that for all intents and purposes is as light as many aluminum jobs. It should be no secret a number of companies offer billet steel flywheels, but with the Tilton billet setup, the flywheel is CNC-machined from chrome moly steel. Unlike other clutches that rely on loose-fitting dowels or bolts to locate the clutch to the flywheel, Tilton utilizes a precision machine step on the flywheel to locate the clutch and provide optimal balance. A step measuring 0.100-inch tall is built into the flywheel. This step is for the clutch friction surface. You’ll note in the photos that all unnecessary material is removed from the flywheel. Obviously, the reason for this is to reduce overall flywheel weight. While Tilton could have machined the flywheel to be lighter, they engineered the mass of the flywheel to provide a good combination of performance and drivabilty. If the clutch/flywheel assembly is too light, drivability on the street suffers. Where many aftermarket flywheels are two-piece designs with separate ring gear assemblies, the Tilton flywheel is one-piece construction. Flywheels for conventional Chevys with two-piece rear main seals are only available in 153-tooth ring gear combinations. This means the flywheel, including the ring gear, measures 12-3/4 or so inches in diameter. In comparison, a 168-tooth flywheel for the same combination will typically measure approximately 14-1/4 inches in diameter. The only time this will become a big consideration for most engines is when the oil pan is an aftermarket job with a big kickout that mandates a large diameter ring gear. Otherwise, the small diameter ring gear setup will work. Keep in mind, too, that the smaller diameter flywheel plays a considerable role in reducing inertia. Recall that “if the weight in a rotating mass is moved closer to the center of the mass then the entire assembly can spin faster.” The lightweight small diameter flywheel allows the engine to spin up quicker. It’s that simple. Finally, Tilton notes that the ST-246 clutch and flywheel are balanced separately from each other, so there is no need to index the clutch to the flywheel. Something else we have to mention is the included hardware: Tilton packages a set of ARP flywheel bolts with the kit and also includes a set of 12-point 3/8-inch aircraft quality bolts and AN-washers to attach the pressure plate to the flywheel. FYI, the clutch to flywheel bolts must be torqued to 35 lb-feet while the flywheel to crank flange bolts must be tightened to 75 lb-feet. Locking compound should be used on the pressure plate bolts, while thread lube on the threads and under the head of the flywheel bolts is recommended. In the end, do these small diameter dual disc systems work? Absolutely. The small diameter dual disc clutch assemblies provide a pedal feel that is actually very light, and more in line with what you might find in a typical four-cylinder economy car. As you can see, Tilton has taken their decades of racing technology and applied it to the street-strip car. Not only is torque capacity increased, pedal pressure is reduced. It’s a win-win situation. And from a quality perspective, you’ll be blown away the moment you open the box. For a closer look, check out the accompanying slideshow.

The flywheel is a small diameter job machined from a chunk of billet chrome moly. There’s a lot of machining here, folks, as you’ll see in the next photos:

The starter ring gear is not a separate piece (which are regularly riveted to the flywheel). Instead, the ring gear is machined directly into the flywheel. FYI, the ring gear has 153 teeth.

The crank flange and clutch locking step in the flywheel are precision machined. This ensures everything fits tightly. Tilton balances the pressure plate and disc setup separately from the flywheel, which means you don’t have to index the clutch to the flywheel.

A step that measures 0.100-inch tall is provided to locate the clutch disc(s) friction surface. As you can see, what isn’t needed isn’t included. That way, they can keep the flywheel weight down to a minimum.

Included with the package is a set of 12-point 3/8-inch aircraft quality bolts and AN-washers. These bolts are used to attach the pressure plate to the flywheel.

Additionally, Tilton includes a set of ARP flywheel bolts in the kit. Obviously, they too are of high quality. Not shown is a clutch alignment tool that Tilton also includes.

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