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Clutch Dust

A look at the variety of clutches that service the drag racing market, from Stock to the supercharged ranks of professional drag racing.

Publication: National Dragster
Author: Galimi, Michael
Date published: July 3, 2015
Language: English
PMID: 54249
ISSN: 04662199
Journal code: NDRG

Your left leg is shaking while the needle on the tach is bouncing wildly as the engine is banging offthe rev limiter. The Tree drops, you sidestep the clutch pedal, the two-step limiter turns off, and away you go as the tires dig in to the starting line, the engine soars to the stratosphere, and the nose of the car points up. The shiftlight flickers, and you instinctively pull the transmission shiftlever to put the box into 2nd gear, and at that point, depressing a clutch may or may not be involved in selecting the next gear.

Automatic cars have become more popular thanks to better transmissions and torque converters, but a manual transmission still offers a competitive and, more importantly, fun alternative. Typically, a Long-style pressure plate/ cover with single-disc clutch is the go-to piece for most Sportsman racers in applications up to 1,000 horsepower. "The McLeod SoftLok has been around since the 1970s and has a wide range of adjustability and applications," said Paul Lee of McLeod Racing. And according to Mike Norcia of RAM Automotive, the easiest way to identify a Long-style clutch are its three levers and coilspring pressure plate.

The Long-style clutch setups offered by both RAM and McLeod allow the user to add counterweight to the levers, which increases the centrifugal load on the clutch as rpm increases. This is in addition to the static load on the clutch plate that can be adjusted by stand height. Mike Norcia of RAM explained, "The Long-style clutch has been around for many years, and it is unique in its design. The lever is mounted in the ring, and it has some centrifugal impact, unlike a diaphragm clutch." He went on to describe that RAM's single-disc, Long-style clutch has a wide range of static base-pressure adjustment, which is determined by the clutch disc (or discs) and other vehicle specifics, like engine size and rpm capabilities.

Black Star Clutch

Moving past Long-style clutches are pedal, centrifugal-assisted, and full-centrifugal clutch assemblies. Multidisc options and many different diameters come into play when going to these race-oriented clutch setups. It is this type of clutch that is found in the high ranks of Sportsman and Professional drag racing, like Top Sportsman, Pro Mod, the alcohol ranks, and even the nitro world. The companies I spoke with for this article cater mostly to bigpower, non-nitro applications.

Choosing the right amount of clutch discs depends on how much slip is produced because you are using the multiple discs to help manage heat. A clutch's diameter is also a part of the equation because the racer not only wants to manage the heat from slip at launch but also prevent slip as the rpm and horsepower increase.

According to Norcia, high rpm requires a smaller diameter, but that also means a smaller tuning window. For a typical Top Sportsman combination, he recommends a 10-inchdiameter clutch, and Super Stock and some Stock applications call for an 8-inch setup. Lee said a common reference for the McLeod Pro Series clutch, which is built in collaboration with Boninfante Racing Clutches, is to run a single disc up to 1,000 horsepower, double discs to 1,400 horsepower, and a triple-disc setup to 3,000 horsepower.

For Bob Molinari of Molinari Racing Products, he works one on one with the customer to find the best clutch for each individual application. "Once a competitor reaches this level of competition, they know what they are looking for, and you help refine the lever configuration and material design," he said. Molinari or one of their dealers works one on one with the racer also on building a clutch in their budget. At this level, the clutches are made with mostly billet components and in some cases titanium, putting the cost significantly higher.

Crower has been designing and manufacturing clutches since 1966, and while the company doesn't offer a Long-style clutch, it does have what it calls the Crowerglide and Crower Pedal clutch assemblies. Both are geared toward hard-core drag racing applications used mostly with Lenco, Liberty, and B&J transmissions.

Roger LeVine of Crower walked me through a variety of clutch setups, like the company's 10.5-inchdiameter automatic/centrifugal clutch in the Nostalgia Funny Car ranks that has six fingers, six springs, and three discs. LeVine reaffirmed that at this level the manufacturer and racer absolutely must work together in order to build the proper clutch assembly for an application because there are so many options.

Bob Sanders of Titan Speed Engineering has been building clutches since 1988 and went through how the Black Star clutches are designed to optimize rigidity, in addition to possessing other features. And like the other clutches, the levers and adjustable stands offer a near infinite amount of adjustability to suit any engine combination in front of the clutch. "There are no two cars that are the same, which makes it so much fun," said Sanders. "You are always trying to balance the clutch with the curve of the engine. It is all related - the fuel delivery, blower (if there is one), and the clutch."

Automatic transmissions might be getting more popular, but manual transmissions and clutchdriven vehicles will always offer a serious amount of fun for the driver as well as the ability to adapt the clutch to the engine and track conditions.

One company is constantly in the field and available at every NHRA Mello Yello Drag Racing Series national event: Hyatt Racing Services. The company is a dealer for many product lines, including a few different clutch companies, such as McLeod. The team can work with customers in selecting the proper setup for any application, but the most unique attribute is the on-site, fullservice center at those national events. The Hyatt rig is a mobile clutch-service center for rebuilding and resurfacing clutches. A racer can also order a clutch before the race and pick it up at the next event, provided the production timeline fits.

Author affiliation:

Michael Galimi is a regular contributor to national publications, including Race Pages, Fastest Street Car, Muscle Mustangs & Fast Fords, Super Chevy, and Chevy High Performance. He is also involved with the National Mustang Racers Association and the National Muscle Car Association to promote street-legal drag racing.