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There's nothing like rowing through the gears in a high-horsepower manual transmission car. But, it's all fun and games until a slipping clutch crashes the party. Luckily, Hays offers clutch and driveline components for just about every popular application. Hays has been building clutch kits for hot rodders since 1958, so they know a thing or two about what works and what's just “good enough”. Consequently, each Hays product is simple, straightforward, and competition proven.
Before you put Hays' six decades of experience to work for you, there's a few things to consider. We'll cover clutch kit types, hub configurations, friction materials, and flywheel styles to help you make an informed decision before your next launch.
For gasoline vehicles, Hays offers three types of clutch kits: Hays Classic, Hays Street 450, and Hays Street 650. The choice depends upon how you use your vehicle. To meet the demands of today's diesel truck enthusiasts, Hays offers their Diesel 650 and Diesel 850 clutch kits.
Here's a handy chart to help you decide on a clutch kit:
If you're looking to replace your factory clutch with a high-quality Hays unit that doesn't wear out your left leg or your wallet, Hays Classic is your clutch. Designed to handle stock to mildly-modified engines, Hays Classic clutch kits include a heavy duty diaphragm that features light pedal effort for easy daily use. The organic friction material and sprung hub ensures smooth, chatter-free engagement that's also gentle on flywheels. The throwback colors and dependable performance are hallmarks of a Hays Classic clutch.
For engines up to 450 horsepower, the Hays Street 450 clutch is for you. It offers more clamping force and a higher horsepower rating than a Hays Classic clutch without sacrificing street manners. The Hays Street 450 clutch features an upgraded pressure plate with up to 30% more clamping force than factory to handle higher horsepower applications. The Hays Street 450 clutch disc utilizes organic friction material surrounding a heavy-duty, 8-spring hub assembly for increased load capacity over stock. The result is smooth, street-friendly operation that won't let you down at the strip.
For the weekend warrior with a serious naturally-aspirated or forced induction/nitrous powerplant under the hood, the Hays Street 650 fits the bill. It combines an uprated pressure plate with 30% more clamping force over stock with sintered metallic disc material for dependable clutch performance round after round. The sintered metallic material is designed to allow a little slip on hard engagement to soften the violent hit to driveline components that's typically associated with metallic clutch materials. Even though the Hays Street 650 Clutches are designed to survive repeated strip use, the extreme-duty sprung hub with polyurethane encapsulated springs keeps the "street" in the Hays Street 650 clutch.
A Hays Diesel 650 clutch is a great upgrade from the stock clutch. They handle up to 650 lb-ft of torque while still maintaining smooth drivability. An upgraded clutch disc increases holding capacity up to 30% over stock while minimizing pedal effort. The organic composite clutch disc features a steel backing for better heat dissipation, extended wear, and quick thermal recovery. A marcel fin disc design improves engagement manners and is ideal for street, towing, and heavy duty use.
The Hays Diesel 850 Clutches turn up the wick from the Diesel 650 clutches by swapping out the organic composite disc for a ceramic button-style clutch disc to handle engines pumping out 850 lb-ft of torque or up to 200 horsepower more than stock. The Hays Diesel 850 clutch pressure plate features 30% more clamping force over stock while keeping pedal pressure manageable. The beauty of the Hays Diesel 850 clutch lies in the Carlisle (Wellman) sintered buttons that allow increased holding capacity for unparalleled performance and longevity, whether it's putting power down or hauling a heavy load.
Before we move on, let's dive a little deeper into clutch disc design and materials:
Sprung hubs help damp engine firing pulses so they don't rattle the transmission gears and make a lot of noise. The springs also absorb shock loads on hard launches. But just like everything, standard sprung hubs have their limits. In high-horsepower, dedicated drag racing applications, an old-school trick was to install a solid hub disc (no springs) and ignore the additional noise and transmission wear.
Rather than resort to a solid hub for high-horsepower applications, Hays uses 6, 8, and encapsulated sprung hubs in their Classic, Street 450, and Street 650 clutch kits. These new designs feature the durability of a solid disc with the smoothness and protection of a sprung hub on the street.
Hays Classic 6-Spring Hub - Absorbs engine firing pulses for smooth operation.
Hays Street 650 8-Spring Hub - Additional springs and internal spring dampers handle higher horsepower and shock loads over standard 6-spring hub.
Hays Street 850 Encapsulated 8-Spring Hub - Springs are encapsulated in polyurethane to offer triple the shock load capacity as standard sprung hubs.
The type of friction material plays an integral role in clutch drivability and holding capacity. Organic composite offers the smoothest engagement and is the most "drivable" material. Most OEM clutches feature organic material as well as Hays Classic and Hays Street 450 clutches. Hays offers sintered metallic material in the Street 650 clutches for higher horsepower applications and repeated drag strip use. (The Hays Diesel 850 clutches feature Carlisle (Wellman) sintered ceramic material to meet the needs of high-torque modified diesel applications.)
Hays Organic Composite Friction Material - Ideal for street and mild strip applications.
Hays Sintered Metallic Friction Material - Best suited to serious street and strip applications.
Hays Diesel 850 Ceramic Friction Material - Heavy-duty diesel applications
Flywheels take a lot of abuse, so Hays offers SFI-certified flywheels for popular applications. The first question is: "steel or aluminum?" Or more accurately, "heavy or light?"
A heavier flywheel (steel) helps heavy cars launch without bogging but requires more horsepower to rev through the gears. A lighter (aluminum) flywheel needs less horsepower to rev but stores less energy for launches. Generally speaking, lighter cars respond well to lighter flywheels, while heavier cars launch better with heavier flywheels.
(It's important to note that a Hays aluminum flywheel still includes a steel friction surface for durability.)
Hays offers steel and aluminum flywheels in different weights for popular applications in both internally-and externally balanced configurations. When choosing a Hays flywheel, be sure to select one that fits the "balance" of your engine. Some engine years have different external "imbalance" specs and require a different counterweight. Some Hays flywheels feature different bolt-on weights for different applications. When in doubt, check with your engine builder before ordering.
Both Hays steel and aluminum flywheels are SFI-certified to ensure safety over OEM flywheels that can shatter during hard launches and under extreme conditions (which is why an SFI-certified bellhousing, such as a Lakewood or Quick Time is always a good idea--and required by some sanctioning bodies).
Hays SFI-Certified Steel Flywheel - Best suited to heavy cars during hard launches.
Hays SFI-Certified Aluminum Flywheel - Great for lighter drag cars and road racing.
As always, Hays tech help is just a phone call away at 1-866-464-6553. Happy gear banging!
