1. Engine Crankshafts Products
  2. sku: 20447248169663891
  3. AUTO SPECIALTIES 520120

AUTO SPECIALTIES 520120 Underdrive Pulley Set

fits model: Street.

520120 Auto Specialties Underdrive Street Pulley Set

( Brand: Auto Specialties ), ( Manufacturer Part Number: 520120 ), ( Part Type: Auto Specialties Underdrive Street Pulley Set ), ( Seller: Summit Racing Equipment )

Review AUTO SPECIALTIES Underdrive Pulley Set fits STREET

The **Auto Specialties 520120 Underdrive Street Pulley Set** is a meticulously engineered, high-performance accessory designed to elevate the driving experience of enthusiasts seeking enhanced throttle response, improved engine efficiency, and a more engaging road feel. This precision-crafted pulley set is specifically tailored for use with high-performance turbocharged and supercharged applications, as well as naturally aspirated engines that demand superior power delivery and reduced lag. Constructed from premium-grade materials, including high-strength steel and advanced composite alloys, the pulley set is engineered to withstand the intense stresses of aggressive driving, high RPM scenarios, and prolonged use under demanding conditions. The set features a unique underdrive configuration, which optimizes the crankshaft s rotational speed, allowing the engine to rev more freely and reducing the strain on the drivetrain while delivering a more linear and responsive power band. This design is particularly beneficial for street-driven turbocharged vehicles, where quick spool-up times and reduced turbo lag can make a noticeable difference in acceleration and overall drivability. The pulley set includes a carefully balanced set of components, including the underdrive pulley, tensioner, and idler pulley, all of which work in harmony to minimize vibration, noise, and wear on the serpentine belt system. Whether installed on a turbocharged performance sedan, a muscle car, or a high-revving naturally aspirated engine, this pulley set is a game-changer for those looking to unlock the full potential of their vehicle s power delivery. Its compatibility with a wide range of applications from daily drivers to track-focused machines makes it a versatile and indispensable upgrade for any automotive enthusiast prioritizing performance, reliability, and a refined driving experience.

**Pros and Cons of buying a Auto Specialties 520120 Underdrive Street Pulley Set**

The **Auto Specialties 520120 Underdrive Street Pulley Set** is designed for performance applications, particularly in vehicles with underdrive pulleys (common in some muscle cars, trucks, and high-performance setups). Below is a detailed breakdown of its advantages and disadvantages.

### **Pros**

1. **Performance Enhancement**

The pulley set is engineered to reduce engine drag, allowing the engine to rev higher and more efficiently. This can improve throttle response, especially in high-performance or modified engines where stock pulleys may be restrictive.

2. **Durability and Quality**

Auto Specialties is a well-regarded brand in the aftermarket performance industry, known for producing reliable and high-quality components. The pulley set is typically made from strong materials (often steel or reinforced alloys) to withstand high RPMs and stress.

3. **Compatibility with Aftermarket Parts**

Many performance enthusiasts use underdrive pulleys in conjunction with other modifications, such as high-flow air intakes, performance cams, or superchargers. This pulley set is designed to work well with such setups, providing a balanced solution for increased horsepower.

4. **Ease of Installation**

The pulley set is generally straightforward to install, especially if you have basic mechanical experience. It usually requires removing the stock pulley and replacing it with the new set, though some applications may require additional adjustments (e.g., belt tensioner alignment).

5. **Cost-Effective Upgrade**

Compared to more extensive engine modifications, replacing the pulley set is a relatively inexpensive way to gain noticeable performance benefits. It s often seen as a "quick win" for those looking to improve drivability without major overhauls.

6. **Reduced Engine Strain**

By reducing the load on the crankshaft, the pulley set can help prolong the life of the engine, particularly in high-torque applications where stock pulleys may wear out prematurely.

7. **Compatibility with Modern Vehicles**

While often associated with older muscle cars (e.g., Ford Mustang, Chevy Camaro, Dodge Challenger), this pulley set can also be used in modern trucks and performance vehicles with underdrive pulley setups, making it versatile for a range of applications.

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### **Cons**

1. **Limited to Underdrive Pulley Applications**

Not all vehicles use underdrive pulleys. If your engine has a standard drive pulley setup, this part will be incompatible, making the purchase unnecessary. Always verify your vehicle s specifications before buying.

2. **Potential for Increased Oil Consumption**

Some drivers report slightly higher oil consumption when using underdrive pulleys, as the crankshaft spins faster, which can increase piston slap and oil burn. This is usually minor but worth monitoring, especially in high-mileage engines.

3. **May Require Additional Modifications**

In some cases, installing underdrive pulleys may necessitate adjustments to the belt tensioner, water pump, or alternator pulleys to ensure proper alignment and prevent binding. This could add to the installation complexity or cost if other components need replacement.

4. **Not a Substitute for Engine Tuning**

While the pulley set improves drivability, it does not compensate for poor engine health or lack of tuning. If your engine is running poorly (e.g., misfires, carbon buildup, or incorrect fuel/air ratios), the pulley set alone won t resolve those issues. A tune or performance chip may still be needed for optimal results.

5. **Noise Considerations**

Some users notice increased engine noise, particularly at higher RPMs, due to the faster crankshaft rotation. While this is often considered a "good" sound for performance enthusiasts, it may not be desirable for those seeking a quieter operation.

6. **Warranty and Return Risks**

Since this is an aftermarket part, it may not be covered under the manufacturer s warranty, and returns could be difficult if installed. Always check the seller s return policy before purchasing.

7. **Potential for Overreving**

While underdrive pulleys allow higher RPMs, they can also make it easier to accidentally overrev the engine if the driver isn t accustomed to the new rev range. This is more of a driving habit issue than a mechanical one but is worth considering.

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### **Conclusion**

The **Auto Specialties 520120 Underdrive Street Pulley Set** is a solid choice for performance-oriented drivers looking to improve throttle response, reduce engine drag, and enhance high-RPM operation in vehicles equipped with underdrive pulleys. It offers a cost-effective way to gain noticeable performance gains with relatively minimal installation effort. However, it is not a universal solution it only benefits specific engine setups and may require additional adjustments or tuning for optimal results.

If your vehicle uses underdrive pulleys and you re looking to push performance without a full engine rebuild, this pulley set is a worthwhile upgrade. Conversely, if your engine lacks underdrive pulleys or you re not planning further modifications, the investment may not yield the expected benefits.

### **Recommendation**

**Buy the Auto Specialties 520120 Underdrive Street Pulley Set if:**

- Your vehicle is equipped with underdrive pulleys (verify compatibility with your engine).

- You re modifying your engine for performance (e.g., adding a cam, supercharger, or high-flow intake).

- You want a simple, affordable way to improve drivability and revving characteristics.

- You re prepared to monitor oil consumption and potentially adjust other pulley-related components.

**Avoid purchasing if:**

- Your engine uses standard drive pulleys (this part will not fit).

- You re not planning any other performance modifications (the benefits may be minimal).

- You prioritize absolute quietness over performance gains.

- You re unsure about installation or lack basic mechanical skills (consult a professional).

For best results, pair this upgrade with a performance tune or chip to ensure the engine runs optimally at higher RPMs. Always follow installation instructions carefully and consider consulting a mechanic if you re unsure about compatibility or fitment.

Details:

Auto Specialties 520120 Pulley Set, Serpentine, Steel, Nitrite Black, Ford, 5.0L, Set. Please hover mouse to image.

part #: 520120 prices

  • $152.99-$266.88

specifications cranshafengin:

  • for models: Street
  • brand: Auto Specialties
  • mpn: 520120
  • part type: Auto Specialties Underdrive Street Pulley Set
  • seller: Summit Racing Equipment

general cranshafengin:

  • condition: New
  • Car Truck Parts Accessories > Engines Engine Parts > Crankshafts

seller cranshafengin:

  • # reviews: 1147125
  • city: Tallmadge, Ohio
  • rating: 99.6%

payments cranshafengin:

  • credit card: Visa
  • other
  • wallet: Apple-pay

offer cranshafengin:

  • quantity: 4
  • started: May 19, 2026
  • availability: In Stock
  • options: Ship-to-home
  • sold: 0

shipping cranshafengin:

  • transit: 2-4 Days
  • class: Economy
  • type: Fixed
  • cost: $0.00
  • service: Economy

returns cranshafengin:

  • time: 30 Days
  • policy: Returns Accepted
  • paid by: Seller
for models: street, part type: auto specialties underdrive street pulley set, seller: summit racing equipment,
category: auto parts > car truck parts accessories > engines engine parts > crankshafts, sku: 20447248169663891,
Auto Specialties 520120 Is Similar To:
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3 offers $152.99–$266.88 USD
  • New. Offer #1 priced at $152.99 + $0.00 shipping estimate = $152.99* total. Auto Specialties Pulley Set, Serpentine, Steel, Nitride Black, Ford, 5.0L, Set.FREE SHIPPING
  • New. Offer #2 priced at $244.59 + $0.00 shipping estimate = $244.59* total. FREE SHIPPING
  • New. Offer #3 priced at $266.88 + $0.00 shipping estimate = $266.88* total. Remote Reservoir : Yes. Power Steering Outlet ID Size : 0.438".FREE SHIPPING

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