How to Choose the Right Clutch for Your Project Car

Motor 1

4 days ago

When piecing together any project car, the proverbial angel and devil rest on opposite shoulders. The first one says take it easy, spend within your means, and keep your ambition reined in.
"
Remember, this is a road car,"
it warns in a sensible tone.
The second voice is a chaos agent. It shouts "
MORE MORE MORE"
in the other ear.
MORE power, MORE tire, MORE money, MORE awesome.
Our Camaro's interior: MUCH hooptie left to unhooptie.
Photo by: Kyle Kinard / Motor1
To pick the perfect aftermarket clutch, you must heed both voices, balancing performance with civility, while leaving enough headroom for your project to evolve down the line. It's a tricky thing to nail, especially with literally hundreds of options available online.
The stakes are high, too: You don't know exactly how well a clutch will work until it's installed on your car. By then, it's too late to wind back the advice of that devil on your shoulder.
Enter the experts at
Centerforce Clutches
. We spoke with Centerforce's director of marketing, Trent McGee, who walked us through the various types of clutches available on the aftermarket and the process of choosing the right clutch for any project car.
What you'll get in the mail from Centerforce: some seriously legit packaging.
Photo by: Kyle Kinard / Motor1
McGee cut through the static for us, separating the forum bro-science from the lessons you should heed.
In full disclosure, Centerforce shipped out a clutch for our
Camaro vs. World project series
, gratis. But they'd have my full endorsement, whether I paid for the parts or not.
For one, Centerforce represents genuine American manufacturing. The company is based in Prescott, Arizona, where all the R&D and manufacturing are done in-house. Their prices are surprisingly competitive, and when the clutch, flywheel, and all ancillary components arrived, I found them to be gorgeously machined and very well packaged. All the documentation, instructions, and hardware you need are in the box.
More hardware than an ACE aisle.
Photo by: Kyle Kinard / Motor1
If you've done a clutch swap on a project car before, you know this is rarely the case. I'll have an actual review of the clutch performance itself, along with a look at the install process, once the Camaro is running. Stay tuned for that one.
But which clutch to choose? Centerforce was a logical place to start. I learned from McGee that Centerforce has been in the business of making performance clutches for 42 years—as long (or longer) than anyone else.
More importantly, Centerforce employees are obsessed with the subject matter and willing to share that expertise. You don't have to take my word for it. Seriously, just give them a call next time you're looking for a clutch; Whether or not you read about it, I'll be buying my next clutch from Centerforce.
Everything in the box is VERY nicely machined and manufactured.
Photo by: Kyle Kinard / Motor1
What follows is a Q&A with McGee, with feedback that applies to the selection of any aftermarket clutch. The key takeaways are legion, but the main point is something that resonates with every decision you'll make about a project car: think very hard about how you'll actually use your car when it's finished, then work backward from there.
If you don't have an endpoint in mind from the beginning, you'll spend a lot more money by the time you've arrived at your destination. Whichever company you decide to buy from, give them a call to help guide your decision, with all the considerations that follow kept in mind.
Photo by: Kyle Kinard / Motor1
[Ed Note: We lightly edited the following conversation for organization, continuity, and clarity]
Kyle Kinard, Motor1: Let's dive in from the top level. What does a clutch do, and why is it so important to pick the right one for our project cars?
Trent McGee, Centerforce Clutches:
So in its simplest form, the clutch is essentially the connection point between the engine and the transmission. The clutch system itself consists of three basic components. You have the flywheel, the clutch disc, and the pressure plate.
The clutch disc itself is sandwiched between the flywheel—which is effectively attached to the engine—and a pressure plate. The pressure plate is a diaphragm, a big spring essentially.
When you're physically pushing on the clutch pedal, you are pushing on that spring and basically engaging or disengaging the pressure plate to the clutch disc.
Motor1: That's a concise explanation, and a good one. We know there's more to it than that, but beyond the basics, a basic question: How do you choose the right clutch for a project?
McGee: Because it's that critical link between the engine and transmission, it's also really critical to choose the correct clutch for your application.
In, say, a daily driver sort of an application, you want something that's nice and smooth, you want something that doesn't take a linebacker's left leg to engage or disengage the clutch.
You also don't want a flywheel that's going to chatter. You want to be able to pull away from a streetlight or a stop sign and not buck. But there are a lot of trade-offs when selecting a clutch.
You can have that super smooth, silky smooth engagement, but those clutches maybe don't have quite the holding capacity that you would need in a higher-performance application.
Motor1: Can you unpack that last part of the equation? Because I think that's critical here.
McGee: What I mean by 'holding capacity' is that clamp load, that mechanical connection between the disc being clamped to the flywheel.
Motor1: How do you increase holding capacity for a performance application?
McGee: Well, you can do that a number of different ways. The easiest thing is to just increase the amount of pressure, increase the amount of force where the clutch disc is sandwiched to the flywheel.
That sounds great in theory, but it becomes very, very difficult to engage and disengage the clutch.
Motor1: That's very annoying to deal with on a day-to-day basis. Been there, done that. What other options do you have?
McGee: Well, we can start playing with friction materials. There are many different types of friction materials out there. Some are more aggressive than others. The more aggressive the friction material, the greater the holding capacity.
Now you've got something that's real grabby, something that is more like an on-off switch, which is once again, a big drawback for a daily driver. You want just a nice, smooth engagement. And so it's all a balancing act, essentially.
Motor1: It always comes back to balance. That's a mistake a lot of us make, isn't it? Getting a clutch that's too aggressive instead of balanced.
McGee: I think the biggest mistake is that people think they need a super aggressive clutch, or they need something with just tons of holding capacity. Well, if it's a track car, that might be the case. But in many cases, truly, it's not a total track car.
'Oh, well, but I also do cars and coffee on Sundays,' a customer will say. 'I like to take the kids out on Sunday drives and stuff like that.'
Well, in those sorts of scenarios, a real aggressive clutch is not a good solution. So what we see a lot is people may be overestimating exactly what they're going to be doing with their car, and leaning a little bit too hard into the performance side of things.
Motor1: What's another common pitfall?
I will say that many people don't build their car all at once. It usually comes in stages. So what I mean by that is you might LS swap your Camaro, for example, but down the road, there might be heads and a turbo.
The caveat to what I was just talking about—being too aggressive with clutch selection—is that if you're planning on crossing that threshold at about 650 lb-ft, you might be better served to go to a twin-disc clutch out of the gate as opposed to doing a single-disc for now and then having to reinvest in a new clutch in the future.
Buying a clutch is really something you only want to do once, so that is something to consider.
Motor1: Can you explain the difference between the single- and twin-disc clutches, and why there's a rough cutoff at about 650 lb-ft where you'd consider stepping from one to the other?
McGee: So basically, a twin-disc clutch actually doubles the amount of friction surface that you have. Instead of a single clutch disc, you now have two.
The torque transfer is divided between those two discs, so there's less load on the individual discs, and yet more friction surface, or just more physical surface for that torque transfer to take place.
Motor1: And that's what we have for the Camaro project.
McGee: Yeah. So in the case of the SST (one of Centerforce's twin-disc clutches), that is a great entry-level twin because it has organic friction material, it has solid hubs. The solid hubs actually make it a little bit more aggressive in terms of engagement, but it's still very, very, very streetable. The only drawback you're going to get with a twin in general, because there's more physical stuff in the clutch assembly itself, it can be a little bit heavier.
We can counteract that by taking weight out of the flywheel. And so there are physical windows cut out of the flywheel itself, and we do that to reduce the amount of overall weight.
The other thing with the twin to keep in mind for anybody that's considering one, is they are a bit noisier. They're noisier mostly because of that floater plate [positioned between the two discs, that's usually keyed into the flywheel via pins or dowels].
And when the clutch is disengaged, the floater plate floats. And so twin-disc clutches have more, what we call, rollover noise. So with the engine running and the transmission neutral and the clutch out, you can hear more noise.
We actually counteract that noise by putting the floater on some spring-loaded bushings that are built into the floater plate itself. And what those bushings do is dampen a lot of that noise. This is, I believe, unique to us.
Motor1: What else is there to consider when selecting a clutch package?
McGee: The other thing I'll say is that the master cylinder bore plays a very, very, very critical role in how the hydraulics operate, because basically the larger the bore, the more fluid you're able to transfer. However, there is such a thing as too much. So really, what I would encourage anybody that's considering an aftermarket hydraulic system to do, is have a conversation with the manufacturer; those guys live and breathe it, they do it all day every day.
Motor1: That's another hack, isn't it? Something I've learned while putting the Camaro project together. Just pick up the phone. Any good company will be able to guide you to the right choice. Turns out the experts know a lot more than I do.
McGee: I would say it's always good to talk to the manufacturer, whether it's us or if it's another clutch company, have a conversation with those guys. They're going to be able to tell you the pros and cons because, once again, a clutch is kind of a delicate balancing act between the performance you need and the drivability.
More on Our Camaro Project
Our Camaro Build's Objective? Keep Porsches on Their Toes
Every Project Starts With a Shell. This Is Ours
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