1. Engine Crankshafts Products
  2. sku: 19580861841972722
  3. MOLNAR 340-4000EF6F

MOLNAR TECHNOLOGIES 340-4000EF6F Forged Crank Pin 4.000 2.125

fits model: 125, Sbm.

340-4000ef6f Molnar Technologies Sbm Forged Crank 4.000 Stroke With 2.125 Pin

( Brand: Molnar Technologies ), ( Manufacturer Part Number: 340-4000EF6F ), ( Part Type: Crank Pin ), ( Performance Part: Yes )

Review MOLNAR TECHNOLOGIES Forged Crank 4.000 Stroke 2.125 Pin fits SBM 125

The **Molnar 340-4000EF6F SBM Forged Crankshaft** is a premium, high-performance component engineered for durability, precision, and reliability in demanding engine applications. Crafted from **SBM (Super Bilateral Molnar) forged steel**, this crankshaft represents the pinnacle of modern forging technology, delivering exceptional strength, fatigue resistance, and dimensional stability under extreme loads. The **4.000-inch stroke** provides a robust foundation for high-output engines, whether in drag racing, street tuning, or professional motorsports, where consistent power delivery and longevity are critical. The **2.125-inch main journal diameter** ensures stable operation and reduced stress on the engine block, while the **4000 series designation** indicates a refined design optimized for high-revving applications, balancing weight and rigidity for superior harmonic balance.

This crankshaft features **Molnar s signature SBM forging process**, which enhances grain flow and internal integrity, minimizing the risk of cracks or failures under extreme conditions. The **fully counterweighted design** minimizes vibration, contributing to smoother operation and extended bearing life, while the **precision-machined surfaces** ensure tight tolerances for optimal fitment with aftermarket and OEM components. Whether paired with a high-performance camshaft, aggressive valve train, or forced induction, this crankshaft is engineered to handle the stresses of aggressive tuning without compromising structural integrity. Its **heat-treated and balanced** construction guarantees consistent performance across a wide RPM range, making it an ideal choice for builders seeking a balance of strength, weight, and reliability in their next-generation engine builds.

### Pros and Cons of buying a Molnar 340-4000EF6F SBM Forged Crank (4.000" Stroke, 2.125" Pin)

#### **Pros**

1. **High-Quality Forged Construction** Molnar cranks are known for their precision-forged steel, which offers superior strength, durability, and resistance to fatigue compared to cast or billet cranks. This reduces the risk of catastrophic failure, especially under high stress or extreme conditions.

2. **Balanced and Smooth Operation** The SBM (Single Bolt Main) design, combined with Molnar s machining processes, ensures excellent balance and minimal vibration. This contributes to smoother engine operation, reduced wear on bearings and rods, and improved longevity.

3. **Precision Engineering** Molnar cranks are designed with tight tolerances and optimized geometry for specific applications (e.g., drag racing, street performance, or endurance racing). The 4.000" stroke and 2.125" pin size suggest this is built for high-torque, high-revving engines, making it ideal for forced-induction or high-compression setups.

4. **Compatibility with High-Performance Engines** The crank is likely designed to work with aftermarket components, including forged rods, pistons, and connecting rods, making it a solid choice for builders pushing performance limits. It may also be compatible with popular engine patterns (e.g., Chevy LS, Ford Modular, or small-block Ford) depending on the application.

5. **Warranty and Support** Molnar offers warranties on their cranks, providing peace of mind against defects in materials or workmanship. Their reputation in the performance market also means reliable customer support and technical assistance.

6. **Durability for Extreme Use** Forged cranks are less prone to cracking or warping under extreme loads, making this crank suitable for applications like drag racing, top-fuel, or heavy-duty street builds where reliability is critical.

7. **Customization Options** Molnar often provides cranks with specific features like counterweights tailored to the engine s needs, which can improve balance and reduce stress on the block and rods.

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#### **Cons**

1. **High Cost** Forged cranks from Molnar are premium products, and this particular crank (especially with a 4.000" stroke) will likely be expensive compared to cast or billet alternatives. The price may be prohibitive for budget-conscious builders or those not pushing extreme performance.

2. **Weight** Forged cranks are heavier than cast or billet cranks, which can add mass to the engine, potentially reducing revving potential or responsiveness in high-RPM applications. However, this is often negligible compared to the benefits of durability.

3. **Limited Availability** Molnar cranks may not be as widely stocked as more common brands, requiring special ordering or purchasing through authorized dealers. This could delay your build timeline.

4. **Specialized Knowledge Required** Installing a high-performance crank like this may require expertise in engine assembly, balancing, and alignment. Improper installation (e.g., incorrect rod length, bearing clearance, or torque specs) could void warranties or lead to premature failure.

5. **Potential Overkill for Mild Applications** If you re building a modestly modified engine (e.g., a mild street tune or light-duty performance build), the cost and complexity of a Molnar crank may not be justified. A cast or billet crank from a more affordable brand might suffice.

6. **Compatibility Issues** Ensure the crank fits your engine s rod length, journal size, and bolt pattern. Some aftermarket cranks require custom rods or other modifications, adding to the cost and complexity of the build.

7. **Maintenance and Inspection Needs** Forged cranks are durable, but they still require regular inspection for wear, cracks, or imbalance, especially in high-stress applications. Neglecting maintenance could lead to catastrophic failure.

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### **Conclusion**

The Molnar 340-4000EF6F SBM forged crank (4.000" stroke, 2.125" pin) is an excellent choice for builders targeting extreme performance, reliability, and longevity in high-stress applications such as drag racing, forced-induction street builds, or endurance racing. Its forged construction, precision engineering, and balanced design make it a top-tier option for those willing to invest in a crank that will withstand the most demanding conditions.

However, the high cost, weight, and specialized requirements may not align with every project. If your build is more modest or on a tighter budget, a cast or billet crank from a reputable manufacturer might be a more practical alternative. Always weigh the performance gains against your budget, application, and long-term goals before making a decision.

---

### **Recommendation**

**Buy this crank if:**

- You are building a high-performance engine (e.g., 1,000 HP, forced induction, or extreme compression ratios).

- Reliability and durability are critical (e.g., racing, towing, or heavy-duty street use).

- You have experience with engine assembly or are working with a trusted mechanic.

- Your budget allows for a premium forged crank without compromising other build components.

**Avoid this crank if:**

- Your project is a mild modification or a budget-conscious build.

- You lack experience with high-performance engine components or assembly.

- You can find a compatible cast or billet crank at a significantly lower cost without sacrificing performance.

- Your engine s rod length or other specifications don t align perfectly with the crank s requirements.

For most extreme performance builds, the Molnar crank is a **strong recommendation** due to its reputation and engineering. For everything else, carefully evaluate alternatives to ensure the best balance of cost, performance, and practicality.

Details:

Crankshaft - 4.000 in Stroke Internal Balance Forged Steel 2-Piece Seal 340 Mains Small Block Mopar Each. Manufacturer: Molnar Technologies.

part #: 3404000ef6f prices

  • $1377.19-$1442.60

specifications cranshafengin:

  • for models: 125, Sbm
  • brand: Molnar Technologies
  • mpn: 340-4000ef6f
  • part type: Crank Pin
  • performance part: Yes

offer cranshafengin:

  • sold: 0
  • availability: In Stock
  • started: March 30, 2026
  • options: Ship-to-home
  • quantity: 1

general cranshafengin:

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

seller cranshafengin:

  • city: San Leandro, California
  • rating: 99.8%
  • # reviews: 125761

payments cranshafengin:

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  • credit card: Discover
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shipping cranshafengin:

  • transit: 2-5 Days
  • class: Standard
  • type: Fixed
  • service: Standard
  • cost: $0.00

returns cranshafengin:

  • time: 30 Days
  • paid by: Seller
  • policy: Returns Accepted
for models: 125, sbm, part type: crank pin, performance part: yes,
category: auto parts > car truck parts accessories > engines engine parts > crankshafts, sku: 19580861841972722,
Molnar Technologies 340-4000EF6F Is Similar To:
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5 offers $1377.19–$1442.60 USD
  • New. Offer #1 priced at $1377.19 + $0.00 shipping estimate = $1377.19* total. Crankshaft - 4.000 in Stroke - Internal Balance - Forged Steel - 2-Piece Seal - 340 Mains - Small Block Mopar - Each. Manufacturer: Molnar Technologies.FREE SHIPPING
  • New. Offer #2 priced at $1442.60 + $0.00 shipping estimate = $1442.60* total. Finish: Natural. Mains: 340.FREE SHIPPING
  • New. Offer #3 priced at $1411.67 + $79.00 shipping estimate = $1490.67* total. 340-3790EB6F Small Block Chrysler -2.100" Rod Pins 3.790 340 2.100 6.123 1850. CHRYSLER SMALL BLOCK FORGED CRANKS.+$79.00 shipping
  • New. Offer #4 priced at $1411.67 + $79.00 shipping estimate = $1490.67* total. +$79.00 shipping
  • New. Offer #5 priced at $1411.67 + $79.00 shipping estimate = $1490.67* total. +$79.00 shipping

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