GM GENUINE PARTS 12642339 Engine Crankshaft

( Brand: Gm Genuine Parts ), ( Manufacturer Part Number: 12642339 ), ( Part Type: Engine Crankshaft ), ( Genuine Oem: Yes ), ( Manufacturer Warranty: 1 Year ), ( Fitment Type: Direct Replacement ), ( Make: Chevrolet ), ( Year: 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 ), ( Parts Included: Only Part Reference 26 On The Diagram Is Included )

Review GM GENUINE PARTS Engine Crankshaft fits 2014–2024

The **GM 12642339 Engine Crankshaft** is a precision-engineered component designed for high-performance and durability in General Motors small-block and performance-oriented V8 applications, including the iconic LS-series engines. Crafted from high-grade forged steel, this crankshaft is engineered to withstand extreme stress, high RPM demands, and prolonged use in both street and racing environments. The design features a robust main journal and rod journal configuration, optimized for smooth operation and minimal vibration, ensuring longevity and reliability even under heavy loads. The crankshaft s counterweights are strategically balanced to reduce harmonic distortion, enhancing overall engine efficiency and reducing wear on critical components like the bearings and connecting rods. This part is compatible with a range of GM engines, including the LS1, LS2, LS3, and LS7, making it a versatile upgrade for both stock and modified setups. Whether used in a high-performance drag car, a muscle car restoration, or a daily driver seeking enhanced power and durability, the GM 12642339 crankshaft delivers a perfect blend of strength and precision. Its seamless integration with GM s engine architecture ensures compatibility with stock or aftermarket components, making it an ideal choice for enthusiasts looking to maximize performance while maintaining reliability. Built to meet or exceed OEM specifications, this crankshaft is a testament to GM s engineering legacy, offering a balance of power, endurance, and ease of installation for mechanics and builders alike.

### **Pros and Cons of Buying a GM 12642339 Engine Crankshaft**

The **GM 12642339** is a crankshaft used in various General Motors engines, including the **LS1, LS2, and LS3** families. Below is a detailed analysis of its advantages and disadvantages.

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### **Pros of Buying a GM 12642339 Crankshaft**

1. **High Quality and Durability**

- GM crankshafts are forged from high-strength steel, ensuring long-lasting performance under high stress.

- The design incorporates balanced counterweights to reduce vibration, improving engine smoothness.

2. **Compatibility with Popular Engines**

- This crankshaft fits multiple **LS-series engines**, including the **LS1 (4.8L), LS2 (6.0L), and LS3 (6.2L)**, making it a versatile replacement option.

- Common in aftermarket builds, performance modifications, and restorations.

3. **Aftermarket and Performance Support**

- Widely available from **OEM suppliers, aftermarket brands (e.g., JE, Scat, Crane), and eBay/Amazon sellers**, ensuring easy sourcing.

- Many performance-oriented crankshafts (e.g., forged, nitrided, or balanced) are available for enhanced durability in high-RPM applications.

4. **Cost-Effective Replacement Option**

- Compared to full engine replacements, a crankshaft swap is significantly cheaper, often ranging from **$300 $1,000 ** depending on brand and modifications.

- Can extend the life of an otherwise salvageable engine.

5. **Warranty and Return Options**

- Reputable sellers (e.g., **Crane, JE, or OEM dealers**) often provide warranties, reducing long-term risk.

- Some aftermarket brands offer **lifetime warranties** on forged crankshafts.

6. **Improved Reliability for Modified Engines**

- If an engine is heavily modified (e.g., forced induction, high RPM tuning), a **performance crankshaft** can prevent catastrophic failure.

- Nitrided or hardened cranks resist wear better than stock units.

---

### **Cons of Buying a GM 12642339 Crankshaft**

1. **Potential Counterfeit or Low-Quality Parts**

- The aftermarket is flooded with **fake or subpar crankshafts**, especially from unverified sellers.

- Poor-quality cranks may **bend, crack, or fail prematurely**, leading to expensive engine damage.

- Always verify the **manufacturer s authenticity** (e.g., check for proper markings, certifications, or seller reputation).

2. **Installation Complexity**

- Replacing a crankshaft requires **specialized tools, machining, and expertise** (e.g., crankshaft alignment, bearing press-fit, and balancing).

- If not installed correctly, it can cause **engine misfires, oil leaks, or premature wear**.

- May require **machine shop assistance**, adding labor costs.

3. **Additional Costs Beyond the Crankshaft**

- **New main bearings** (if not reusing old ones)

- **Rod bearings** (if the rods are being replaced)

- **Seals, gaskets, and oil pump** (if worn)

- **Balancing and machining** (if the crank is new but the engine block isn t perfectly prepped)

- These extra costs can **double or triple the total expense**.

4. **Risk of Block or Engine Damage**

- If the engine block has **cracks, warping, or excessive wear**, a new crankshaft alone won t fix underlying issues.

- A **block inspection** (via magnaflux or pressure testing) is often necessary before installation.

5. **Limited Longevity in Extreme Applications**

- While high-quality cranks (e.g., **forged, nitrided**) improve durability, **extreme builds (e.g., 1,000 HP turbocharged engines)** may still require **custom cranks or additional reinforcement**.

- Some aftermarket cranks may not be **fully compatible** with aggressive modifications (e.g., oversized rods).

6. **Potential for Misalignment or Vibration Issues**

- If the crankshaft is **not properly balanced or aligned** with the engine block, it can cause **excessive vibration, rod knock, or bearing failure**.

- Requires **precision machining** to ensure a perfect fit.

7. **Sourcing Risks from Untrusted Vendors**

- Some sellers on **eBay, Facebook Marketplace, or Craigslist** may offer **used or salvaged cranks** with unknown histories (e.g., previous cracks, wear, or modifications).

- **OEM vs. Aftermarket Confusion** Some "GM 12642339" listings may actually be **LS1 cranks (part # 12642339) but not the correct version for LS2/LS3**, leading to fitment issues.

---

### **Conclusion**

The **GM 12642339 crankshaft** is a **practical and cost-effective solution** for restoring or upgrading an LS-series engine, especially when sourced from a **reputable manufacturer**. Its **high durability, compatibility with popular engines, and aftermarket support** make it a strong choice for both **stock and modified applications**.

However, the **risks of counterfeit parts, installation complexity, and additional costs** mean that buyers must **conduct thorough research** before purchasing. **Prioritizing quality over price** and ensuring **professional installation** are critical to avoiding costly failures.

---

### **Recommendation**

1. **Buy from a Trusted Source**

- **OEM GM dealers** (for genuine parts)

- **Reputable aftermarket brands** (e.g., **Crane, JE, Scat, Eagle, or Holley Performance**)

- Avoid **unknown sellers** unless they provide **certificates of authenticity, warranties, and proper documentation**.

2. **Verify Compatibility**

- Confirm the **exact engine model** (LS1, LS2, LS3) and **crankshaft specifications** (journal size, counterweight design).

- Some **LS1 cranks (12642339) may not fit LS2/LS3 engines** due to **different rod journal sizes**.

3. **Inspect the Engine Block**

- Before purchasing, ensure the **block is in good condition** (no cracks, warping, or excessive wear).

- Consider a **block inspection** (via **magnaflux or pressure test**) if the engine has seen high mileage or modifications.

4. **Budget for Additional Components**

- **New main bearings** (if not reusing old ones)

- **Rod bearings** (if rods are being replaced)

- **Seals, gaskets, and oil pump** (if worn)

- **Machining/balancing services** (if required)

5. **Professional Installation is Highly Recommended**

- Crankshaft replacement is **not a DIY job for most mechanics**.

- **Crankshaft removal/installation**

- **Bearing press-fit**

- **Balancing and alignment**

- **Final engine assembly**

6. **Consider a Performance-Upgraded Crankshaft**

- **Forged crankshafts** (e.g., **JE 12642339-1, Crane LS3 crank**)

- **Nitrided or hardened surfaces** (for extra wear resistance)

- **Balanced and polished** for smoother operation

7. **Check for Warranty Coverage**

- Some aftermarket cranks come with **lifetime warranties**, which can provide **peace of mind** against premature failure.

---

### **Final Verdict**

The **GM 12642339 crankshaft is a solid choice** for **LS-series engine restorations and performance builds**, provided it is **purchased from a trusted source, installed professionally, and paired with compatible components**. While risks exist (primarily from **counterfeit parts and improper installation**), the **benefits in reliability and cost savings** make it a **worthwhile investment** for the right application. **Prioritize quality over price** to avoid costly engine damage down the line.

Details:

Changed My Mind. Just Didn't Like it. With turbocharger. Found a Better Price.

part #: 12642339 prices

• $812.34-$819.06

specifications cranshafengin:

• for years: 2014-2024
• brand: Gm Genuine Parts
• mpn: 12642339
• part type: Engine Crankshaft
• genuine oem: Yes
• manufacturer warranty: 1 Year
• fitment type: Direct Replacement
• make: Chevrolet
• year: 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024
• parts included: Only Part Reference 26 On The Diagram Is Included

returns cranshafengin:

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

offer cranshafengin:

• sold: 0
• availability: In Stock
• quantity: 1
• options: Ship-to-home
• started: April 13, 2026

shipping cranshafengin:

• cost: $0.00
• class: Standard
• carrier: FedEx
• service: FedEx Ground / FedEx Home Delivery
• type: Fixed
• transit: 9-15 Days

payments cranshafengin:

• wallet: Paypal
• other
• credit card: Mastercard

seller cranshafengin:

• rating: 99.0%
• city: Garland, Texas
• # reviews: 30921

general cranshafengin:

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

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