Posted By John Katz, June 25, 2012 in E-News, Engine & Drivetrain
Meanwhile, manual-shift enthusiasts are upgrading to modern units packing more heavy-duty horsepower capacity—and more gear ratios.
“The generation that is now in their 60s can afford to build the cars that they wanted to build when they were in high school,” said Dick Hill, sales manager for Centerforce Clutches in Prescott, Arizona. And while those folks are not usually looking to build a race car, “they do want a four- or five-speed manual transmission,” he said.
More surprisingly, the trend extends beyond muscle cars and into traditional hot rods as well.
“I have friends who are building Deuce roadsters and they are putting LS motors in them, with a five- or six-speed manual transmission,” Hill said. “There are people who put Cadillac V-8s in 1949–1951 Mercs, and they want a stick. They want a three-pedal car. So that, too, is contributing to the growth of the high-performance clutch market.”
Hot rodders who already own or have owned multiple cars are now looking for something different.
“It’s like the people who buy their first Harley, they want it with every doo-dad they can get, where older bikers are turning back to the Knucklehead or even Flathead motors,” Hill said. “It’s the same with the hot rodder who already has two or three or four toys in the garage. The newest toy is going to be a stick car. And it’s for the same reason that someone will buy a brand-new Camaro, put 1,000 horsepower in it, and drive it on the street while blowing cold air and playing tunes. They want a manual not because they’re going to race it, but because they can have it. That’s what we hear all the time: ‘Because I can.’”
Rating the Ratios
American Powertrain of Cookeville, Tennessee, sells a broad range of high-performance drivetrain components, from complete crate engines to driveshafts and pedals. The company also distributes Tremec transmissions.
“The hot market right now is for the Magnum six-speed in a classic muscle car,” said Gray Frederick. “The Magnum is Tremec’s replacement for the T-56 is the aftermarket version of what you would get in a new Shelby GT500 or Camaro SS.” Frederick added that people are putting them into classic Mustangs Cougars, Camaros Firebirds, Barracudas and Challengers.
“The cars that people spend the most money on are the cars that [are] getting Magnum six-speeds,” Frederick added.
The Magnum is available with two sets of ratios, with the closer-ratio unit being the more popular of the two.
“The wide-ratio box has a 0.5 overdrive, which is very tall; a lot of engines can’t pull that much overdrive,” Frederick said.
But when it comes to overdrive, isn’t more better?
“That’s a myth,” Frederick said. “You can say, ‘Alright, I’m at the ragged edge of my cam, where if I’m on flat ground I can hold 70 mph all day.’ In a perfect world, that would be great. [I]n the real world, at some point you’re going to have to slow down for construction, and then speed up again; or you’re going to hit a rise, or something else that causes your engine to run out of breath. [T]hen you’re going to have to shift and that’s what you’re trying to avoid.
“You want to put it in sixth gear and leave it sixth gear,” he continued. “You don’t want to run down the highway at your cam’s peak performance, which would be 3,000–4,000 rpm. But you do want an rpm where your engine can pull your car up hills, and pass without dropping a gear. If every time you put your foot in the gas the engine lugs and you have to shift, that becomes very inefficient. We’re helping the customer understand that, even on the highway, you want to stay in your powerband. Otherwise the overdrive doesn’t do you any good.”
Frederick recommends the wide-ratio unit mostly for torquey big blocks.
“A Pontiac 455 will pull a stump out of the ground at 800 rpm; it doesn’t have trouble pulling a car at whatever rpm you’re running,” he said. “A Mopar 440 and some other big blocks with a lot of low-end grunt can usually handle the taller overdrive, too. And of course we’re dealing with a lot of electronically fuel-injected (EFI) engines now, and most of them have computers that can cope with low rpm very well.
They can retard the spark, they can meter the fuel differently, they can do all kinds of things.
“We help the customer choose a rearend ratio and a gear set that’s going to give them the best performance, from top to bottom,” Frederick said.
Pedal Pressure Another concern, according to Hill of Centerforce Clutches, is the physical effort once associated with a high-performance clutch.
“Our customers all ask, ‘How stiff is the pedal?’” he said. “That’s why we’ve been very successful, whether it’s a single-disc clutch for mild upgrade vehicle, or dual-disc unit that can hold 1,300 lbs./ft. of torque, we’ve been very successful in making them streetable.”
The average consumer, Hill said, could climb into a car with a Centerforce dual-disc clutch, push the pedal to the floor, and not realize that the car was modified.
“[T]he person who has a $75,000 Camaro or Corvette wants race-car performance without the race-car effort, so this is pretty significant,” he said.
Still, selecting the optimal clutch for any particular application is a complex task best left to experts.
“There are different linings and different friction materials on the pressure plate,” Hill said. “Heat is a factor. The first thing you have to know is how the vehicle is going to be used. Drag racers realize they are going to drive their car until they break it, where hot rodders don’t beat their cars up as bad. They are very proud of their cars and they want to drive them, not break them. And unless the car has been tubbed, a street machine generally runs smaller tires, so you want to tune the clutch for that.”
McLeod Racing of Placentia, California, offers its RST and RXT Street Twin clutches, both double-disc units that hold up to 1,000 horsepower, with the pedal pressure of a stock clutch, said President Paul Lee. Contributing to this low effort—and to easier installation—are McLeod’s hydraulic release bearings, “which fit most applications, replacing worn and/or outdated mechanical linkages,” he said.
“We’re selling more clutches for vehicles from the 1960s and 1970s, and installing a new hydraulic clutch in one of these cars can significantly reduce pedal effort,” said Rich Barsamian, national sales manager for Advanced Clutch Technology (ACT) in Lancaster, California. The company also offers a wide range of clutches for GM, Ford and Mopar applications, each rated for torque at the crankshaft.
When installing an aftermarket clutch, Barsamian suggested, “be sure to use the right amount of lube on the input shaft—it is possible to use too much. Be sure parts are free from dirt and oil, and washed in a non-petroleum-based cleaner such as acetone, alcohol or brake cleaner. Be sure to follow the correct torque and tightening sequence when installing the clutch cover—and do not use impact tools.”
Thanks for reading Part 3 coming up.