7 Best 400 Cranks for 350 Block (Researched and Compared)

Building a stroker 350 with a 400 crank is a classic way to increase displacement and torque. But not all cranks are created equal. We researched manufacturer specs, industry standards, and aggregated owner feedback to compare the top options. This guide covers steel vs. cast, journal sizes, stroke lengths, and balance requirements. Each product is evaluated for performance, durability, value, ease of installation, and safety. Here are our findings.

1. Eagle Specialty Products 4340 Forged Steel Crankshaft: Best Overall

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In our evaluation, the Eagle 4340 forged steel crank stands out for its combination of strength and reliability. Based on owner feedback and spec sheets, this crank handles 600+ horsepower builds without issue. The 3.75-inch stroke is ideal for a 383 or 406 stroker. It comes with 2.100-inch rod journals, compatible with standard 350 rods after minor clearancing.

However, it is not a budget pick. The forged steel construction adds weight and cost. Some owners reported needing external balancing for certain harmonic dampers and flexplates. Skip this if your build is a mild street engine under 400 hp or if you are on a tight budget. For serious power, this is a top contender.

• 4340 forged steel construction for high strength and fatigue resistance
• Precision ground journals with radiused fillets for reduced stress risers
• Includes internal balance weight configuration for neutral balance applications

Pros: Exceptional strength for high-horsepower builds; Consistent quality control from a trusted brand
Cons: Heavier than some cast options, may require balance adjustments

2. Scat 9000 Series Cast Steel Crankshaft: Best Value

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We compared the Scat 9000 series against more expensive forged options and found it offers impressive bang for the buck. Based on owner feedback, it performs reliably in street and mild race engines up to 500 hp. The cast steel construction is stronger than cast iron but less durable than forged. It comes internally balanced for most applications, simplifying installation.

However, we caution against using this crank in engines with sustained high rpm (over 6500) or forced induction beyond 8 psi. Some owners noted that the counterweights are not as heavy as forged cranks, potentially requiring mallory metal for extreme builds. Skip this if you are building a high-boost turbo motor or a drag-only race engine. For a solid street stroker, it is a great choice.

• Cast steel for good strength at a lower price than forged
• Fully counterweighted for smooth operation
• Precision ground journals with micro-polished surfaces

Pros: Excellent value for the performance level; Good balance and finish out of the box
Cons: Not suitable for extreme high-rpm or high-boost applications

3. GM Performance Parts 400 Crankshaft (Cast Iron): Budget Pick

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In our research, this GM cast iron crank is the most affordable way to get a 3.75-inch stroke into a 350 block. It is essentially a stock 400 crank, so it works for a basic rebuild or a low-budget stroker. Owner feedback indicates it is fine for engines under 400 hp with conservative driving.

But we must stress its limitations. Cast iron is substantially weaker than steel, and this crank is not internally balanced. It requires external balancing with specific harmonic balancer and flexplate. Also, the 2-piece rear seal design is incompatible with later 1-piece rear seal blocks without an adapter. Skip this if you plan any performance upgrades or have a 1-piece rear seal block. It is strictly for budget builds where cost is the only concern.

• Factory GM cast iron construction for standard rebuilds
• 3.75-inch stroke for stroker applications
• 2-piece rear seal design (requires adapter for 1-piece blocks)

Pros: Lowest cost option for a budget build; Genuine GM part, easy to source
Cons: Cast iron is brittle and not for high performance; Requires 2-piece rear seal conversion or adapter

4. Callies Performance Products Compstar 4340 Forged Crank: Premium Pick

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Based on manufacturer specs and owner feedback from high-end builders, the Callies Compstar is one of the finest 400 cranks available. It is CNC machined from 4340 billet steel and gun-drilled for optimal oil flow and reduced weight. In our evaluation, this crank is ideal for engines exceeding 700 hp or with high-rpm operation.

However, its premium price puts it out of reach for many. Unless you are building a serious race engine or a high-boost forced induction motor, you likely won’t need this level of strength. Some owners noted that the lightweight design can make balancing more critical. Skip this if your build is under 500 hp or you are on a moderate budget. For those chasing every last horsepower, it is an excellent choice.

• Gun-drilled rod journals for oiling and weight reduction
• CNC machined from 4340 billet for maximum strength
• Lightweight design reduces rotating mass

Pros: Extremely strong and lightweight; Superior oiling with gun-drilled passages
Cons: High price may be overkill for mild builds

5. K1 Technologies 4340 Forged Crankshaft: Top Rated

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We evaluated the K1 Technologies crank as a strong competitor to Eagle and Scat. Based on owner feedback, it delivers reliable performance in street/strip builds up to 650 hp. The fully counterweighted design helps reduce vibration. It is forged from 4340 steel, offering a good balance of strength and weight.

However, a few owners noted that the crank required additional balancing when paired with lightweight rods or pistons. Also, the price is higher than Scat but lower than Callies. Skip this if you need a budget option or if your build is purely stock. For a moderate performance stroker, it is a solid choice.

• 4340 forged steel with fully counterweighted design
• Precision ground and micro-polished journals
• Includes internal balance weight configuration

Pros: Excellent strength-to-weight ratio; Smooth running with full counterweights
Cons: Some owners report need for minor balancing tweaks

6. Procomp Electronics 400 Cast Steel Crank: Entry Level

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In our research, the Procomp crank is the most affordable steel option, but it comes with compromises. Owner feedback is mixed: some report acceptable performance in low-power builds, while others cite out-of-round journals or poor balancing. We recommend it only for very mild street engines under 400 hp.

We advise against using this crank in any performance application. The cast steel is less durable than forged, and quality control issues mean you may need to have the crank machined before use. Skip this if you want reliability or plan any power adders. It is an entry-level product for budget-restricted builds where performance is not a priority.

• Cast steel material for basic stroker builds
• Affordable alternative to forged cranks
• Internal balance configuration for easier installation

Pros: Low price point for a stroker crank; Comes with 1-piece rear seal compatibility
Cons: Quality control can be inconsistent; Not recommended for high horsepower or high rpm

7. ATK High Performance 400 Crankshaft (Remanufactured): Eco Pick

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We included the ATK remanufactured crank for those seeking an eco-friendly option. Based on owner feedback, it works for a stock rebuild of a 400 engine or a budget stroker. It is magnafluxed and reground, but it is still cast iron with the same limitations as a new GM cast iron crank.

However, we found that quality depends on the core condition. Some owners reported needing additional machine work. Also, the 2-piece rear seal limits compatibility. Skip this if you need a high-performance part or a 1-piece rear seal. It is a niche product for cost-conscious builders who prioritize recycling.

• Remanufactured from OEM 400 cast iron cores
• Magnafluxed and inspected for cracks
• Reground journals to standard undersizes

Pros: Environmentally friendly reuse of cores; Lower cost than new cast iron
Cons: Limited availability and core return required; Not for performance use

Frequently Asked Questions

Can I use a 400 crank in a 350 block without modifications?

Typically, a 400 crank (3.75-inch stroke) requires clearancing of the 350 block for rod clearance. The connecting rods will hit the bottom of the cylinder bores unless the block is notched. Also, you may need to use smaller rod journals (2.100-inch) or aftermarket rods. Additionally, the crankshaft may require balancing adjustments. It is not a direct bolt-in.

What is the difference between internal and external balance?

Internal balance means the crankshaft is balanced with no additional weight on the harmonic balancer or flexplate. External balance requires a specific heavy balancer and flexplate. Most 400 cranks were externally balanced from the factory. Aftermarket cranks often offer internal balance weights. Check your engine’s balance requirement before purchase.

Should I choose a forged steel or cast steel crank?

Forged steel is stronger and more durable, suitable for high horsepower and high rpm. Cast steel is cheaper and adequate for mild street builds up to about 500 hp. For most stroker builds, a forged crank is recommended for reliability. Cast iron is only for low-performance budget builds.

Will a 400 crank increase my engine displacement?

Yes, using a 400 crank (3.75-inch stroke) in a 350 block with a standard 4.00-inch bore gives a displacement of 377 cubic inches (383 with 4.030 bore). For a 400 block (4.125 bore), it yields 406 cubic inches. It is a common stroker combination.

What connecting rods do I need with a 400 crank in a 350 block?

You need rods with a 2.100-inch big end journal (or 2.000 if using a small journal crank). Many builders use 5.7-inch or 6.0-inch rods. Piston selection depends on rod length and deck height. It is best to mock up the assembly to ensure clearance.

Our Verdict

After researching and comparing, our top pick is the Eagle Specialty Products 4340 Forged Steel Crankshaft for its proven strength, reliability, and value for performance builds. For budget-conscious builders, the Scat 9000 Series Cast Steel Crankshaft offers an excellent balance of cost and capability. Choose based on your horsepower goals and budget.