1. Engine Crankshafts Products
  2. sku: 20397054267868721
  3. POWERBOND DAYCO SX-3912

POWERBOND BY DAYCO SX-3912 Engine Harmonic Balancer Cylinder 5.7L V8

fits model: Jimmy. make: Gmc. year: 1970–1991.

Sx-3912 Powerbond By Dayco Engine Harmonic Balancer For 1970-1991 Gmc Jimmy 5.7l V8 Cylinder Ct

( Brand: Powerbond By Dayco ), ( Manufacturer Part Number: SX-3912 ), ( Item Weight: 11.1100 ), ( Ipn: C536 37-29 ), ( Placement On Vehicle: Engine Cylinder Block ), ( Compatible Year: 1991 1990 1989 1988 1987 1986 1985 1984 1983 1982 1981 1980 1979 ), ( Core Charge: Free No Core Charge ), ( Type: Engine Harmonic Balancer ), ( Fitment Type: Direct Replacement ), ( Bundle Description: 1 Pc Genuine Dayco Engine Harmonic Balancer )

Review POWERBOND BY DAYCO Engine Harmonic Balancer Gmc 5.7l V8 Cylinder Ct fits JIMMY 1970–1991

The **Powerbond Dayco SX-3912 Engine Harmonic Balancer** is a high-performance, precision-engineered replacement part designed specifically for the iconic **1970 1991 GMC Jimmy** equipped with the legendary **5.7L (350 cubic inch) V8 engine**, including models featuring the **LS1, LS3, or older small-block Chevy configurations**. This balancer is a critical component in maintaining smooth engine operation by dampening vibrations generated by the crankshaft s rotational forces, thereby reducing harshness, prolonging drivetrain longevity, and enhancing overall drivability. Crafted from **high-strength steel** and reinforced with **Dayco s proprietary rubber compound**, the SX-3912 is engineered to withstand the demanding stresses of high-performance applications, whether your GMC Jimmy is a daily driver, a weekend cruiser, or a modified muscle machine pushing serious horsepower. Its **precision-balanced design** ensures minimal vibration transfer to the engine mounts and firewall, which is particularly beneficial for vehicles with aftermarket exhaust systems, heavy loads, or aggressive engine modifications. The balancer features a **robust rubber insert** that provides superior damping characteristics, absorbing harmonic vibrations more effectively than stock components, while the **durable steel housing** resists warping and deformation under extreme conditions. Installation is straightforward, requiring only basic tools, and the part is designed to fit seamlessly with the stock crankshaft pulley bolt pattern, ensuring a secure and reliable connection. Whether you're restoring a classic Jimmy to its original glory or pushing it to the limits with a turbocharged or nitrous-injected engine, the **Powerbond Dayco SX-3912** is an indispensable upgrade that delivers professional-grade performance and durability, keeping your engine running smoothly for miles to come.

### Pros and Cons of Buying a Powerbond Dayco SX-3912 Engine Harmonic Balancer for a 1970 1991 GMC Jimmy 5.7L V8

#### **Pros:**

1. **Compatibility** The SX-3912 is specifically designed for GM small-block V8 engines, including the 5.0L (305ci) and 5.7L (350ci) variants used in the GMC Jimmy from 1970 to 1991. This ensures a proper fit without modifications.

2. **Durability** Powerbond and Dayco are reputable brands known for producing high-quality harmonic balancers. These units are typically made with reinforced rubber and steel components, reducing the risk of premature failure compared to OEM parts.

3. **Reduced Vibration and Noise** A worn or failing harmonic balancer can cause excessive vibration, rattling, and even engine damage over time. A new SX-3912 will smooth out engine operation, improving ride comfort and longevity.

4. **Prevents Serious Damage** If the existing balancer is cracked, warped, or spinning freely, it can lead to catastrophic failure (e.g., a broken balancer core damaging the crankshaft or timing components). Replacing it proactively avoids costly repairs.

5. **Easier Installation** The SX-3912 is a direct bolt-on replacement, requiring no machining or customization. Most mechanics can install it in a few hours with basic tools.

6. **Warranty Coverage** Both Powerbond and Dayco offer warranties (typically 1 2 years), providing peace of mind against early failure due to defects.

7. **Cost-Effective Upgrade** While slightly more expensive than an OEM balancer, the SX-3912 is often more affordable than repairing damage caused by a failing balancer.

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#### **Cons:**

1. **Higher Upfront Cost** A quality aftermarket harmonic balancer will cost more than an OEM replacement (typically $100 $200 vs. $50 $100 for an OEM part). However, this is often justified by longevity.

2. **Potential for Counterfeit Parts** Some sellers may offer knockoff "Powerbond" or "Dayco" balancers that are poorly made. Always purchase from trusted retailers (e.g., RockAuto, Summit Racing, or authorized dealers) to avoid subpar quality.

3. **Requires Professional Installation** While straightforward, improper installation (e.g., misalignment, incorrect torque) can lead to premature wear or failure. If unsure, have a mechanic perform the replacement.

4. **Limited Lifespan Compared to OEM (in some cases)** While aftermarket balancers are durable, they may not last as long as an OEM unit in a well-maintained engine. However, this is rare with reputable brands like Powerbond/Dayco.

5. **May Not Fit Modified Engines** If your GMC Jimmy has been heavily modified (e.g., forged internals, custom crankshafts, or aftermarket balancing), the SX-3912 might not be ideal. In such cases, a custom balancer may be needed.

6. **Rubber Degradation Over Time** Even high-quality balancers will eventually wear out due to heat and vibration. Expect to replace it again in 50,000 100,000 miles, depending on driving conditions.

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### **Conclusion and Recommendation**

The **Powerbond Dayco SX-3912 harmonic balancer is a strong choice** for a 1970 1991 GMC Jimmy with a 5.7L V8, provided it is purchased from a reliable source and installed correctly. The benefits superior durability, reduced vibration, and prevention of engine damage far outweigh the minor drawbacks, such as the higher upfront cost.

**Recommendation:**

- **Buy it** if your current balancer is cracked, spinning freely, or showing signs of wear (e.g., excessive vibration, rattling, or oil leaks).

- **Install it professionally** to ensure proper alignment and torque.

- **Avoid counterfeit parts** by sticking to well-known retailers.

- **Monitor its condition** during regular maintenance checks, as even high-quality balancers will eventually need replacement.

For most owners, this is a **worthwhile investment** that extends engine life and improves drivability. If your balancer is still in good condition, there s no urgent need to replace it, but proactive replacement is wise if you notice any issues.

Details:

Dayco Engine Harmonic Balancer for 1970 1991 GMC Jimmy 5.7L V8 Cylinder ct: Status: In Stock.

specifications cranshafengin:

  • for models: Jimmy
  • for makes: Gmc
  • for years: 1970-1991
  • brand: Powerbond By Dayco
  • mpn: Sx-3912
  • item weight: 11.1100
  • ipn: C536 37-29
  • placement on vehicle: Engine Cylinder Block
  • compatible year: 1991 1990 1989 1988 1987 1986 1985 1984 1983 1982 1981 1980 1979
  • core charge: Free No Core Charge
  • type: Engine Harmonic Balancer
  • fitment type: Direct Replacement
  • bundle description: 1 Pc Genuine Dayco Engine Harmonic Balancer

returns cranshafengin:

  • paid by: Seller
  • time: 30 Days
  • policy: Returns Accepted

shipping cranshafengin:

  • service: Standard, Expedited
  • cost: $0.00
  • type: Fixed
  • class: Standard, Expedited
  • transit: 4-6 Days

offer cranshafengin:

  • started: May 16, 2026
  • sold: 0
  • availability: In Stock
  • options: Ship-to-home
  • quantity: 2

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  • credit card: Discover

general cranshafengin:

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

seller cranshafengin:

  • city: Indianapolis, Indiana
  • # reviews: 658028
  • rating: 99.6%
for models: jimmy, for makes: gmc, for years: 1970-1991, item weight: 11.1100, placement on vehicle: engine cylinder block, compatible year: 1991 1990 1989 1988 1987 1986 1985 1984 1983 1982 1981 1980 1979, core charge: free no core charge, type: engine harmonic balancer, fitment type: direct replacement, bundle description: 1 pc genuine dayco engine harmonic balancer,
category: auto parts > car truck parts accessories > engines engine parts > crankshafts, sku: 20397054267868721,
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