EN40B Billet Crankshafts: Why Serious Engine Builds Are Moving Beyond 4340
If you are building a high-boost, high-RPM engine that needs to survive real abuse—not just dyno glory—the crankshaft material and manufacturing process matter. Spool’s new range of EN40B billet stroker crankshafts is purpose-built for extreme performance engines, delivering exceptional fatigue resistance, torsional strength, and an outstanding response to nitriding.
We now offer EN40B billet longer-stroke crankshafts for the following platforms: Toyota 2JZ, Nissan RB (RB25/RB26), Nissan CA18, and Nissan SR20.
What Is EN40B and Why Does It Matter?
EN40B is a high-grade nickel-chromium-molybdenum alloy steel commonly specified in motorsport and other demanding engineering applications where fatigue resistance and core strength are priorities. In crankshaft form—especially when combined with a correctly controlled nitriding process—EN40B is valued for:
- Excellent fatigue life under cyclic loading (high cylinder pressure, repeated acceleration events)
- High torsional strength to resist twist under big torque
- Outstanding nitriding response for a hard, wear-resistant surface while retaining a tough core
- High-RPM stability where harmonics and sustained load become a real issue
The result is a crankshaft material choice that suits the reality of modern performance builds: more boost, more grip, more heat, and more time spent at load.
True Billet vs “Billet” Cranks: The Difference You Should Care About
Not all “billet” crankshafts are created equal. A true billet crank is machined from solid core stock, then heat treated and finished to specification. This differs from approaches that begin with a near-net forging/casting blank that is then “finish machined”.
Spool EN40B crankshafts are manufactured with a performance-first process:
- CNC machined from EN40B billet core stock
- Heat treatment to specification
- Precision nitriding for surface hardness and wear resistance
- Final grinding and balancing for accuracy and smooth high-RPM operation
This manufacturing approach is designed to deliver consistent, repeatable strength and dimensional integrity—especially important as power levels and engine speeds climb.
EN40B vs 4340: A Practical Comparison for Performance Engines
4340 remains a proven performance crankshaft material and is widely used across the industry. EN40B is generally chosen when the goal is to step up to a premium material that excels under extreme cyclic load and nitriding.
| Feature | EN40B Billet Steel | 4340 Billet Steel |
|---|---|---|
| Typical Use Case | Motorsport / Extreme performance | Performance automotive |
| Fatigue Resistance | Exceptional | Very good |
| Torsional Strength | Very high | High |
| Nitriding Response | Outstanding | Good |
| Surface Wear Resistance (post-nitride) | Very high | High |
| High-RPM Stability | Excellent | Very good |
| Best Fit | Extreme boost, sustained RPM, high cylinder pressure | Most high-performance street/track builds |
If your build is intended for sustained track time, roll racing, drag competition, or a large-frame turbo setup where cylinder pressure is the limiting factor, EN40B is a logical upgrade.
Why a Longer Stroke Crankshaft Changes the Entire Build
A longer-stroke crankshaft increases engine displacement and typically improves torque and response—particularly in the low to mid-range. In turbocharged applications, this often translates to:
- Earlier boost onset (more exhaust energy earlier in the rev range)
- Stronger mid-range torque for improved acceleration and drivability
- Greater power potential when the supporting turbo/fuel system is correctly sized
The right stroker combination should be selected as a system: crank stroke, rod length, piston compression height, pin specification, clearancing requirements, and intended RPM range.
Platforms Available: 2JZ, RB, CA18, SR20
Spool EN40B billet stroker crankshafts are available for key enthusiast platforms where demand for reliable power is high:
- Toyota 2JZ (stroker configurations for serious boost and torque)
- Nissan RB (RB25/RB26 stroker options for responsive RB28-style builds)
- Nissan CA18 (stronger bottom-end foundation for boosted CA builds)
- Nissan SR20 (ideal for high-output SR builds where durability matters)
Explore the range here:
Billet Crankshafts
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Stroker Kits
What to Expect During Installation
Stroker assemblies can require additional checks during build-up. Depending on your block casting, rod choice, and stroke, minor clearancing may be required. A competent engine builder will verify:
- Rod-to-block and rod-to-sump rail clearance
- Counterweight clearance
- Main bearing clearances, thrust clearance, and end-float
- Piston-to-valve clearance and deck height (stroker-dependent)
- Balancing and harmonic control appropriate to the target RPM
If you are unsure which crankshaft or kit suits your intended power band and RPM limit, contact Spool with your build goals and we can point you in the right direction.
FAQ: EN40B Billet Crankshafts
Is EN40B “better” than 4340 for crankshafts?
“Better” depends on the application. 4340 is an excellent, widely used performance material. EN40B is typically chosen as a premium upgrade when fatigue resistance, high-RPM durability, and nitriding performance become higher priorities—common in extreme turbo builds and motorsport use.
Do EN40B crankshafts need nitriding?
For high-performance crankshafts, nitriding is a major advantage because it increases surface hardness and wear resistance while preserving core toughness. Spool EN40B crankshafts are specified with a nitrided finish as part of the manufacturing process.
Will a stroker crank make my turbo spool earlier?
In many turbocharged builds, increasing displacement improves low and mid-range torque and can help build boost earlier, particularly when the turbo and cam package are sized appropriately. Final results depend on the full combination and tune.
Do I need different rods and pistons with a longer stroke crank?
Often, yes. Stroker combinations typically require a matched rod length and piston compression height to achieve the desired deck height and clearance. That is why many stroker setups are sold as complete kits or are paired with custom pistons.
What engines do Spool EN40B billet crankshafts suit?
Spool EN40B billet longer-stroke crankshafts are available for Toyota 2JZ, Nissan RB (RB25/RB26), Nissan CA18, and Nissan SR20 platforms. Availability and stroke options vary by engine.
How do I choose between 4340 and EN40B?
If your build is a high-performance street or occasional track application, 4340 is often an excellent choice. If your goals include extreme boost, sustained high RPM, competition use, or you are building for maximum durability under high cylinder pressure, EN40B is the premium option.
