Introduction: Unlocking 80+ Horsepower on Your Hellcat

Installing an aftermarket pulley on a Hellcat is one of the most effective bolt-on modifications for serious horsepower gains. By reducing the size of the supercharger pulley, you increase boost pressure, forcing more air into the engine. With the proper supporting modifications and a custom tune, owners have reliably achieved 80 to over 100 rear-wheel horsepower increases. This guide provides a detailed, step-by-step installation process, along with critical tips to ensure safety and maximum performance. Whether you’re a seasoned DIY mechanic or a first-time modifier, following these instructions will help you transform your Hellcat’s power delivery.

Before diving in, understand that an aftermarket pulley alone is not a standalone upgrade. To safely handle the additional boost, you must also consider fuel system capacity, intake temperatures, and engine management. Tuning is mandatory; without recalibrating the ECU, the extra boost will push the engine beyond its factory limits, risking detonation and internal damage. We recommend pairing your pulley swap with a quality tuner and supporting mods like a thermostat, colder spark plugs, and a larger heat exchanger.

Choosing the Right Aftermarket Pulley

Aftermarket pulleys for Hellcat superchargers come in various diameters, typically ranging from 2.85 inches down to 2.65 inches. A smaller pulley delivers more boost but also increases stress on the supercharger and fuel system. Common sizes and their approximate boost gains:

  • 2.85-inch pulley: +2–3 psi, around 40–50 whp gain
  • 2.75-inch pulley: +3–4 psi, around 60–70 whp gain
  • 2.65-inch pulley: +4–5 psi, 80+ whp gain (requires upgraded fuel system)

Brands like ATI Performance, RIP Superchargers, and IMS offer high-strength pulleys made from 6061-T6 aluminum or even chromoly steel. Look for pulleys with a precision-machined hub that fits the supercharger snout without excessive play. Always verify compatibility with your Hellcat model year (2015–2023). The RIPP Supercharger pulley page is a solid resource.

Tools and Materials Needed

Gather all tools before starting to avoid interruptions. The following list covers the essentials for a safe and efficient installation:

  • Aftermarket pulley kit (with pulley bolt and washer if included)
  • Socket set (metric and SAE; 10mm, 13mm, 15mm, 18mm commonly needed)
  • Torque wrench (ft-lb and in-lb ranges)
  • Pulley puller / installer set (3-jaw or specific Hellcat tool)
  • Ratcheting wrenches (for tight spaces)
  • Breaker bar (for stubborn bolts)
  • Belt tensioner tool (or long breaker bar to relieve tension)
  • Safety glasses and mechanic’s gloves
  • Shop rags and brake cleaner
  • Thread locker (medium-strength Loctite)

Optional but recommended: a scan tool or boost gauge to verify performance after installation. Invest in a high-quality pulley puller designed for pressed-on supercharger pulleys to avoid damaging the snout.

Preparation Steps

Park and Cool the Engine

Park your Hellcat on a level, well-lit surface. Allow the engine to cool completely — ideally overnight. A hot engine increases risk of burns, and thermal expansion can make pulley removal more difficult. Disconnect the negative battery terminal to prevent accidental battery shorts or electrical faults.

Remove the Engine Cover

The factory engine cover is secured by several bolts (typically 8mm). Use a socket or ratcheting wrench to remove them. Lift the cover straight up; it may be snug due to grommets. Set it aside in a safe place free of dirt or grease.

Access the Supercharger Pulley

Next, remove any components blocking access to the supercharger pulley. This usually includes the intake tube (from air box to throttle body). Loosen the clamps and gently work the tube out. Depending on your model, you may also need to temporarily remove the coolant reservoir cap (not the reservoir) and lift it aside, or unbolt a small bracket. Use a Hellcat forum for model-specific removal tips.

Once the intake tube is out, locate the serpentine belt routing diagram (usually on a label near the radiator). Using a breaker bar or belt tensioner tool, rotate the tensioner counterclockwise to relieve belt tension. Slip the belt off the supercharger pulley and route it out of the way. Note: you may need to remove additional idler pulleys or brackets to gain full clearance. Keep all fasteners organized in labeled bags.

Removing the Stock Pulley

Use a Proper Pulley Puller

The Hellcat supercharger pulley is pressed onto the snout; it cannot be removed by hand. Secure a pulley puller (three-jaw or a dedicated Hellcat puller) behind the pulley hub. Tighten the puller’s center bolt evenly until the pulley pops free. Apply steady pressure — do not use impact guns as they can damage the supercharger bearings. If the pulley is stubborn, apply heat to the hub with a heat gun (not a torch) to expand the metal slightly. Wear gloves and safety glasses during this step.

Inspect the Supercharger Snout

Once the stock pulley is off, clean the snout with brake cleaner and a lint-free rag. Check for any burrs, scoring, or metal shavings. The snout surface must be smooth and free of debris to ensure a proper press fit for the new pulley. If you see signs of wear, consider having the snout professionally polished or replaced before proceeding.

Also inspect the supercharger shaft seal. Any leaking oil or debris indicates a failing seal — replace it now to avoid future downtime.

Installing the Aftermarket Pulley

Align and Press

Coat the inside of the new pulley’s bore with a thin layer of anti-seize or light oil (per manufacturer instructions). Place the pulley onto the supercharger snout, aligning the keyway (if present) or ensuring it’s centered. Use a press tool or the puller in reverse (installer mode) to apply even pressure until the pulley is fully seated. Do not hammer it; use a dedicated installer kit. The pulley should sit flush against the snout shoulder. Check that the pulley bolt hole is aligned correctly (if a bolt is required).

Torque Specifications

Install the new pulley bolt (if supplied) using medium-strength thread locker. Tighten to the manufacturer’s specified torque — typically between 35–45 ft-lb for an aftermarket bolt. Do not overtighten; the soft aluminum snout can strip. Use a calibrated torque wrench for precision. If no bolt is used (press-fit only), proceed to reassembly.

Reassembly

Reinstall the serpentine belt. Ensure the belt routing matches the stock diagram. Many aftermarket pulleys are smaller, so you may need a shorter belt. Consult the pulley kit’s instructions for the correct belt length. If the belt is too long, it will slip; too short may not fit. Proper tension is critical for avoiding belt squeal or failure.

Reattach any brackets, the intake tube, and the engine cover. Torque all fasteners to factory specs (refer to repair manual). Reconnect the battery, ensuring the terminals are tight.

Testing the Installation

Start and Idle Check

Before starting, double-check all connections and look for any loose tools or rags in the engine bay. Start the engine and let it idle for 30 seconds. Listen for any unusual noises — whining from the supercharger is normal, but grinding or knocking indicates a problem. Check for belt squeal by gradually revving the engine to 2,000 rpm. If squealing occurs, verify belt tension and alignment.

Test Drive

Take the car for a short test drive at moderate throttle. Gradually increase boost as you become confident. Install a boost gauge or use a data logging tool (e.g., HP Tuners) to monitor boost pressure and air/fuel ratios. A proper tune is essential; the car will run lean without calibration, risking engine damage. Visit a trusted tuner like Hemi Tuning for a remote or dyno tune.

Tips for Success and Common Pitfalls

  • Always tune: Never run a smaller pulley without a retune. The factory ECU cannot compensate for high boost.
  • Supporting mods: Upgrade your fuel system (lower and upper pumps, injectors) for pulleys below 2.75 inches. Also consider a catch can to reduce oil vapors.
  • Monitor heat: Smaller pulleys raise intake temperatures. An aftermarket heat exchanger and low-temp thermostat help prevent heat soak.
  • Check for belt alignment: Misalignment causes belt shredding. Use a straightedge across pulleys to verify.
  • Log data: Log knock counts, fuel trims, and boost after installation. Even with a tune, adjustments may be needed.
  • Professional help: If you’re uncomfortable with any step, hire a Hellcat-specialized shop. The cost is worth the peace of mind.

Potential Risks and Considerations

Installing a smaller pulley increases supercharger speed and heat. At extreme boost levels (above 12 psi), the factory supercharger’s rotor pack can flex, leading to contact or failure. Upgrading to billet rotors or a larger supercharger may be necessary for sustained high power. Additionally, the engine’s connecting rods and pistons have limitations; beyond 800 wheel horsepower, forged internals become advisable. Always research your year’s weak points — for example, 2015 Hellcats have lighter rods than later models.

Warranty issues: Aftermarket modifications void the powertrain warranty. Keep factory parts for reinstallation if needed. Some dealers may deny claims even for unrelated issues.

Conclusion

An aftermarket pulley is a gateway to substantial power gains on your Hellcat. The step-by-step process outlined here — from selecting the right pulley to final testing — will help you achieve 80+ horsepower safely. Remember that success depends on proper installation, a quality tune, and supporting modifications. With careful planning and attention to detail, your Hellcat will transform into a formidable high-performance machine. For additional guidance, join online communities such as the Hellcat Forum or consult reputable tuning shops. Happy wrenching!