Street Fighter: S-Series Twin-Disc From Monster Clutch Co.

Street Fighter: S-Series Twin-Disc From Monster Clutch Co.

Driving a stock vehicle with a manual transmission is pretty effortless on any modern car– the hydraulic actuation from the slave cylinder is very smooth and almost effortless compared to a mechanical linkage of muscle cars from years ago. However, when you start adding power, things can get a little tricky. Now that the stock clutch can’t hold the added power, it’s time to upgrade. And while some may still associate a stiff clutch pedal with high-performance applications, that’s no longer the case with a modern clutch system. Now you can get a unit like Monster Clutch Companies’ S-Series twin-disc clutch that retains a light pedal feel and will still hold massive amounts of horsepower and torque.

Recently we unveiled our latest project vehicle, a 2000 Pontiac Firebird we call the Dirty Bird. This WS6 has seen better days, and just about every component on the car needs to be replaced, including the clutch. And while this car may look bone stock, it has a little secret that will increase the LS1’s power output to 500 horsepower and 500 lb-ft of torque. These numbers will certainly surpass the holding capabilities of the factory stock clutch forcing us to find a solution to our problem. We found the answer to our dilemma with the help of Monster Clutch Co.

Single vs. Multi-Disc Clutches

Monster Clutch Co. specializes in high-performance clutches for GM LS engines, and while it does offer others for Dodge and Ford vehicles, GM is the bulk of the company’s lineup. It also provides several different clutch types, like single-, twin-, and triple-disc configurations. With all of these options, you might be wondering why we chose the S-Series twin-disc, and it comes down to durability and drivability.

Monster offers a single-disc clutch that is rated for more than enough holding power for what we need. The problem with single-disc units that increase capacity over stock is they tend to be somewhat grippy, making street driving a challenge. If this car was going to see limited street use, then an aggressive single-disc clutch makes sense because we are well under the maximum power level. However, we plan on daily driving this manually-shifted ‘Bird, which makes the S-Series twin-disc clutch much more appealing.

We talked with Steve Addison, the owner of Monster Clutch Company, to get the details on twin-disc clutch technology and how it’s changed the game.

Addison said, “Multi-disc clutches have allowed customers to have their cake and eat it too — gone are the days of super-heavy clutch pedals that build your left calf muscle into something that makes you walk in a circle. Multi-disc units allow us to increase capacity by distributing the load over multiple friction surfaces; by doing this, we can decrease the plate load and bearing load, which provides for a stock-like pedal. Additionally, this also benefits heat dissipation, as your friction areas are increased substantially versus a traditional single-disc unit.”

The Monster S-Series Twin-Disc

The S-Series is the only carbon organic-base twin-disc clutch on the market that can handle severe abuse; this unit will hold up to 700 horsepower and 700 lb-ft of torque at the wheels. But the best part about this clutch is the ability to retain the stock driving characteristics.

Addison said, “The S-Series units are designed for customers who want their cars to behave like they’re stock but be able to handle substantially more power, all this while allowing them to thoroughly abuse them without fear of failure.”

Monster’s LT1 flywheel is a work of art, and the company takes pride in building everything in Texas. We think it’s fantastic as well.

But, you might be thinking, “How is that possible?” It’s pretty simple: Monster starts with a factory GM LT1 pressure plate and then modifies the lift/release and the plate load. These changes increase performance while leaving a clutch pedal that feels like a stock F-body. An added bonus to this design is a clean release for lightning-fast shifts up to 8,000 rpm with factory hydraulics in place.

Another secret to this design is the carbon organic-based material Monster uses in the S-Series.

“The S Series single-disc units utilize pure Kevlar frictions, while the twins and triples utilize a very high carbon content organic friction. The organics are not to be confused with the frictions of old, or the current guys using cheap overseas parts,” Addison explains. “This friction works very well under abuse and can take a tremendous amount of heat without fading or failure — this is due to the high carbon content. Additionally, all S-Series clutches are designed for longevity in mind, not just being abused and retaining factory driving characteristics.”

The S-Series clutch that we used is rated at 700 horsepower and 700 lb-ft of torque at the wheels.

While our S-Series twin-disc clutch is rated up to 700 horsepower and 700 lb-ft of torque, Monster has other options, as well, including a twin-disc rated up to 1,150 rear wheel horsepower. If you need a clutch that will handle even more power, Monster offers its S-Series triple-disc clutch. Addison said, “When stepping up to our triple-disc, we like to have all the information in front of us, not just a power number. A good rule of thumb is if you want the feel of a stock setup and take abuse over the 700 wheel horsepower mark or more; you want to move to the S-Series triple.”


After talking to Addison, we were excited to get the S-Series twin-disc in the Firebird. If you’ve never installed a clutch before, it’s not that involved. Just be sure to take your time and if you have any questions, be sure to ask before moving on.

To pull the T56 transmission out of an F-body, you will need to remove the Y-pipe, torque arm, and driveshaft. You will also want to remove the shifter to make this process easier. You will also need to unhook the hydraulic hose going to the slave cylinder. Be sure to unplug all of the wires going to the T56 before lowering it to avoid pulling on the sensors and adding stress to the wiring.

If you never removed a T56 from an F-body, it not a big deal. You will need to remove the y-pipe, torque arm, shifter, and driveshaft. The hardest part of the entire process is getting to the bellhousing bolts.

With everything unhooked, you will now unbolt the transmission from the bellhousing. The top bolts are cramped and we used several extensions so that we could get to them. After you get all of the bolts out, double-check to make sure nothing is still connected to the transmission. If you’re in the clear, you can pull the unit carefully and lower it down. A transmission jack is a lifesaver and highly recommended.

With the transmission out of the way, you can now remove the bellhousing, pressure plate, clutch, and flywheel. This is also a perfect time to inspect your rear main seal. As you can see, ours was leaking, so we replaced it. It’s crucial to check for any oil leaks from the back of the engine because you don’t want oil contaminating a new clutch. The only other thing that needs to be removed is the pilot bearing; we used a slide hammer to pull ours.

With the factory clutch and flywheel out of the way, we then removed the pilot bearing and replaced it with the one Monster supplies. We also yanked the rear cover and replaced the gasket and the rear main seal.

After several cans of brake cleaner, the block was clean for the first time in years. It was now time to install the flywheel and clutch assembly. The first step was to install the new pilot bearing before mounting the flywheel to the crank with the supplied bolts. Monster suggests using red Loctite to ensure the hardware never backs off.

Monster marked the flywheel and all of the spacers with green marks, so you know exactly how everything lines up.

You will want to torque the flywheel down in three phases: the torque specs are 15 ft-lbs for the first pass, 37 ft-lbs for the second, and 74 ft-lbs for the final pass. The torque sequence is 1-4-6-2-5-3 for six-bolt flywheels. After you clean the clutch discs off with a rag and brake cleaner, you can line everything up with the supplied alignment tool before bolting it down. The pressure plate, like the flywheel, is also torqued in three phases: the torque specs are 20 ft-lbs for the first pass, 40 ft-lbs for the second, and 52 ft-lbs of torque for the last pass, with a sequence of 1-4-6-2-5-3.

With the flywheel torqued down, we installed the first clutch disc using the supplied alignment tool.

Check That Gap

With everything bolted down, it’s time to measure the clearance for the release bearing. This is a crucial step and should not be skipped even if you are using the factory bellhousing. 

The WS6 slave cylinder and throwout bearing had seen better days. Fortunately, Monster Clutches included a replacement with the clutch.

With the bellhousing bolted up, you will measure from the fingers on the pressure plate to the outside of the bellhousing face. Write this figure down as measurement A. You will also record the distance from the slave cylinder release bearing to the transmission mounting surface for measurement B. You will then subtract A and B, which will give you the gap. 

There are three essential things to note here: calipers are the preferred measuring method because the air gap is critical. Secondly, the measurement for A will never be smaller than B. 

To get an accurate measurement, we bolted a flat piece of metal to the bellhousing. We then measure from the finger to the metal strip using a set of digital calipers. This is a critical step, so take your time and do it right.

Finally, It’s important to make sure the release bearing is fully compressed on the slave cylinder for measurement B. The black base of the bearing should touch the aluminum base of the slave, if it’s not you can crack the bleeder and push it down the rest of the way. If you don’t address this you can get an inaccurate measurement which can lead to some headaches. You will then subtract A and B, which will give you the gap.

Monster includes a worksheet so you can record your measurements and write them down. We had a .186 gap, which was good according to Monster’s specs.

According to Monster, they like to see no less than a .0625-inch gap and no more than a .200-inch with their units. We were in spec with a .186-inch gap, so we proceeded to put the car back together. However, if you are running an aftermarket bellhousing and the gap is too big, you can shim the throwout bearing. Tick Performance makes shims specific for this purpose.  

With everything buttoned up and back together, we bled the hydraulic side of our slave cylinder. Once we were happy with the pedal, it was time to start breaking in the clutch.

Breaking It In

We know how hard it is to actually read instructions and be patient while breaking in a new product. But listen, this step is super important and needs to be done for the longevity of the S-Series clutch. Monster Clutch Co. recommends a 500-mile break-in period of pure street driving — not road trips.

While we did hit the back roads for a few quick photos, Monster recommends that you break the clutch in driving around town. We won’t count these miles, but you can tell by the picture that everything went according to plan.

“We urge you to drive your vehicle to and from work if this commute includes stop-and-go traffic. This will allow you to repeatedly work the pedal with an extended cooldown period while working or after you get home,” Addison explained. “It’s all about heat cycles and bedding the friction surfaces to allow the frictions the best chance at a long life. Do not skip this step!”

Monster Of A Warranty Program

Like most elite performance manufacturers, Monster Clutch Co. stands behind its products.

“We offer a 12-month warranty against manufacturer’s defects. This applies to all units manufactured by us regardless of whether you’re driving it daily or racing it every weekend, Addison explained. “We also offer a ‘no questions asked’ 12-month add-on warranty that allows the consumer one full rebuild/replacement of their clutch for the add-on warranty price within the first year of ownership. This is very popular with our racers as it essentially is an uber discounted rebuild that’s expedited through our system.”

We love the attention to detail on the S-Series twin-disc package. You can find little monster “easter eggs” all over the product.

While we are still on the dreaded break-in period with our new clutch, we have yet to beat on it. We can tell you that the S-Series twin-disc pedal is just as smooth as the factory one and we are excited to get to the racetrack to see how the WS6 does. We only have 428 more break-in miles to go. Ugh…. Are we there yet?

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About the author

Brian Havins

A gearhead for life, Brian is obsessed with all things fast. Banging gears, turning wrenches, and praying while spraying are just a few of his favorite things.
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