Why Upgrade to a Metco 2.75-Inch Pulley on Your Hellcat?

The supercharged 6.2-liter Hemi in the Dodge Challenger and Charger Hellcat is already a formidable powerplant, but even factory muscle can be improved. Swapping the stock supercharger pulley for a smaller diameter unit—like the Metco 2.75-inch pulley—is one of the most effective bolt-on upgrades. By reducing the pulley diameter, the supercharger spins faster relative to engine speed, increasing boost pressure and airflow. The result is a significant gain in horsepower and torque, often 50–70 wheel horsepower depending on supporting modifications.

Metco Motorsports is a well-known manufacturer in the high-performance community, producing CNC-machined pulleys with precision indexing and anodized finishes. Their 2.75-inch pulley is designed specifically for the Hellcat’s IHI supercharger, offering a direct fit without requiring additional brackets or spacers. This guide provides a comprehensive, step-by-step installation procedure that prioritizes safety, accuracy, and minimal downtime.

Understanding Supercharger Pulley Ratios and Boost

Before diving into the wrenching, it helps to understand what the pulley swap does. The stock Hellcat supercharger pulley is approximately 2.99 inches in diameter. Swapping to a 2.75-inch pulley increases the drive ratio from roughly 3.0:1 to about 3.27:1. This change spins the supercharger approximately 9% faster at the same engine RPM, yielding an additional 2–3 psi of boost. With proper fuel and tuning, this additional boost translates into tangible power gains across the rev range.

Keep in mind that higher boost levels increase heat, fuel demand, and strain on components. A conservative tune, along with proper octane fuel (preferably 93 or E85), is essential to avoid knock and maintain reliability. For maximum safety, many owners also upgrade the fuel injectors and low-pressure fuel pump when running this pulley. However, the installation of the pulley itself is a mechanical task that can be performed in a well-equipped home garage with basic hand tools.

Tools and Materials Needed

Gather the following items before starting. Having everything on hand prevents unnecessary trips during installation and keeps the process efficient.

  • Metco 2.75-inch supercharger pulley kit – part number M-275-HC. Includes the pulley and necessary hardware (bolts, thread locker).
  • 1/2-inch drive socket set – metrics: 10mm, 13mm, 15mm, 18mm sockets. Also a 12-point 8mm socket for the pulley bolts.
  • Torque wrench – capable of 15–45 lb-ft.
  • Ratchet and extensions – 3-, 6-, and 12-inch extensions.
  • 3/8-inch drive impact gun (optional but speeds removal).
  • Screwdrivers – flathead and Phillips for wire connectors and clips.
  • Trim removal tools – for prying plastic covers without damage.
  • Blue thread locker (Loctite 242) – pre-applied on Metco bolts, but extra is good.
  • Brake cleaner and shop towels – for cleaning the shaft and pulley bore.
  • Safety goggles and mechanic gloves.

Preparation and Safety

Workspace Setup

Park the Hellcat on a level concrete surface. Ensure the engine is cool to the touch to avoid burns. Disconnect the negative battery terminal with a 10mm socket to prevent accidental starter engagement or electrical shorts while working near the supercharger.

Remove the Engine Cover and Air Intake

The factory plastic engine cover simply lifts off after removing two 10mm screws at the rear. Next, remove the resonator and intake tube assembly by loosening the clamps and disconnecting the mass air flow (MAF) sensor connector. This provides clear access to the supercharger inlet and the pulley area. Set the intake components aside on a clean surface.

Relieve Belt Tension

Use a 18mm socket or wrench on the belt tensioner pulley. Rotate the tensioner clockwise to release tension from the serpentine belt. Slip the belt off the supercharger pulley first; then carefully release the tensioner. Routing the belt around the other pulleys to keep it out of the way. It is not necessary to remove the belt entirely unless you prefer full access.

Removing the Stock Supercharger Pulley

With the belt off, you can now see the stock pulley. The Hellcat supercharger pulley is secured with six 12-point bolts that require an 8mm 12-point socket. Do not attempt to use a standard hex socket or you risk stripping the bolt heads.

Step 1: Remove the Six Pulley Bolts

Using the 8mm 12-point socket on a ratchet or impact gun, remove all six bolts in a star pattern to prevent warping. Keep the bolts sorted; you will not reuse them with the Metco pulley.

Step 2: Pull Off the Stock Pulley

The stock pulley slides off the supercharger snout by hand. If it is stuck due to corrosion, gently tap the back of the pulley with a rubber mallet while pulling outward. Do not pry on the supercharger casing or use a jaw puller that could damage the pulley hub threads. The hub is splined, and the pulley should come off with minimal force.

Step 3: Clean the Supercharger Snout

Wipe the exposed snout with a clean shop towel and brake cleaner to remove any debris, oil, or old thread-locker residue. The Metco pulley fits tightly; cleanliness is critical to maintain concentricity and prevent vibration.

Installing the Metco 2.75-Inch Pulley

The Metco pulley arrives with new bolts and a film of thread locker already applied. Verify that the bolts are the correct length (approximately 20mm) for the snout depth. Do not use longer bolts; they could bottom out and crack the supercharger housing.

Step 1: Install the Pulley Hub (If Separate)

Some Metco kits include a separate hub that bolts to the supercharger snout, and then the pulley outer ring slides over it and is retained by bolts. Check your kit instructions. For the standard M-275-HC kit, the pulley is a single piece with pre-drilled holes. Align the pulley with the splines and slide it on by hand. It should seat flush against the supercharger flange.

Step 2: Apply Additional Thread Locker

If desired, apply an extra drop of Loctite 242 to each bolt before insertion. This is a safety measure against bolt loosening due to supercharger harmonics. Do not use high-strength red Loctite, as removal later will be extremely difficult.

Step 3: Install Bolts and Torque to Spec

Hand-start all six bolts. Using a torque wrench, tighten in a cross pattern to 20 lb-ft (27 Nm). Do not exceed 22 lb-ft; overtightening can strip the aluminum threads in the supercharger hub. Confirm each bolt is fully seated and there is no gap between the pulley flange and the supercharger snout face.

Reassembly and Belt Installation

Step 1: Route the Belt Over the New Pulley

Check the belt routing diagram on the underside of the hood or consult your service manual. With the tensioner still relieved by the 18mm wrench, route the belt over the new pulley. Ensure the belt ribs align perfectly in the pulley grooves. Release the tensioner slowly to seat the belt.

Step 2: Inspect Belt Tension and Alignment

Rotate the engine by hand (using a 18mm socket on the crankshaft balancer bolt) to check belt tracking. The belt should run centered on all pulleys. Listen for any rubbing or misalignment. If the belt rides too close to the edge of the new pulley, you may need a slightly shorter or longer belt. The stock belt length (80.5 inches) usually works with a 2.75-inch pulley, but verify that the tensioner is within its operating range. If the tensioner is bottomed out, switch to a belt that is 1/2 inch shorter.

Step 3: Reinstall Air Intake and Engine Cover

Reattach the intake tube and resonator, ensuring all clamps are tight and the MAF sensor is connected. Replace the engine cover and secure with the two screws.

Final Checks and First Startup

Reconnect Battery and Inspect

Reconnect the negative battery terminal. Turn the key to the ON position without starting the engine. Listen for the fuel pump prime. Check for any loose tools or rags left in the engine bay.

Start the Engine and Idle

Start the engine and let it idle for 30 seconds. Listen for unusual whining (other than normal supercharger whine) or metallic sounds. The belt should not chirp or squeak. If it does, recheck belt tension and alignment.

Check for Leaks and Heat Cycle

Inspect around the pulley bolts for any oil seepage (unlikely). Drive the vehicle gently for 10–15 minutes, keeping boost low to allow the engine and supercharger oil to reach operating temperature. Return to the shop and let the engine cool completely. After cooling, re-torque the six pulley bolts to 20 lb-ft. This ensures the bolts are fully seated after the first heat cycle.

Tuning and Performance Considerations

Installing the 2.75-inch pulley alone will increase boost approximately 2–3 psi over stock. However, the Hellcat ECU cannot compensate for the additional airflow without a custom tune. Running the pulley with a factory calibration can cause high knock retard, reduced timing, and potential engine damage. A proper tune from a reputable shop (such as Hemi Performance or DiabloSport) is strongly recommended. The tuner will adjust fuel tables, ignition timing, and supercharger bypass settings to safely extract maximum power.

For those planning to run the pulley on pump gas, upgrading to ID1050x injectors and a Fuel Abyss Divider (or Fore fuel system) is common. This ensures adequate fuel delivery at the higher boost levels. Many owners pair the Metco pulley with a 180-degree thermostat, colder spark plugs, and an improved heat exchanger for sustained performance.

Maintenance and Long-Term Tips

  • Belt inspection: Check belt condition every oil change. The smaller pulley increases belt wrap and flex, which can accelerate wear.
  • Pulley bolt torque: After the first 500 miles, recheck pulley bolt torque. Some tuners recommend a follow-up re-torque after 1,000 miles.
  • Boost monitoring: Install a boost gauge to verify peak boost matches expected values. You should see around 14–15 psi at high RPM (versus stock 11.6 psi).
  • Data logging: If you have tuning software, perform a datalog to ensure knock count remains zero and fuel trims are within safe range.

Conclusion

The Metco 2.75-inch pulley installation is a rewarding upgrade that unlocks significant power from the Hellcat’s supercharged V8. By following this detailed step-by-step process, you can complete the swap in a weekend with basic tools and return to the road with confidence. The key to success lies in proper torque, belt alignment, and a supporting tune. When done correctly, this modification transforms the Hellcat into an even wilder machine, delivering punchy acceleration and a glorious supercharger whine. For further reading and product sourcing, visit Metco Motorsports for official pulley specs and Hellcat Forum for community experiences and tuning tips.