Spool Nissan RB25/6 - RB28 EN40B Stroker Crankshaft

Spool Nissan RB25 / RB26 – RB28 EN40B Billet Stroker Crankshaft

The Spool EN40B RB28 stroker crankshaft is engineered for Nissan RB25 and RB26 builds where increased capacity, torque, and extreme durability are required for high-boost and high-RPM applications.

Using a 77.7 mm stroke, this crankshaft increases displacement to approximately 2.8 litres, delivering a substantial improvement in torque, response, and overall engine performance compared to the factory crankshaft.

Why EN40B?

EN40B is a nickel-chromium-molybdenum alloy steel widely used in high-end motorsport and aerospace applications due to its outstanding fatigue resistance and core strength.

When nitrided, EN40B develops an exceptionally hard wear surface while maintaining a tough, ductile core—making it ideal for engines subjected to:

• High cylinder pressure

• Sustained high RPM

• Aggressive boost and ignition strategies

For serious RB builds, EN40B provides a clear step up in long-term reliability over traditional crankshaft materials.

True Billet Construction

The Spool RB28 EN40B crankshaft is a true billet crankshaft, precision CNC-machined from solid EN40B core stock.

This is not a cast or forged blank.

Manufacturing process:

1. CNC-machined from EN40B billet core stock

2. Heat treated

3. Precision nitrided for maximum surface hardness and wear resistance

4. Final ground and fully balanced

The result is a crankshaft with exceptional dimensional accuracy, torsional strength, and fatigue life.

Performance Benefits

Increasing stroke to 77.7 mm delivers meaningful gains in usable power across the rev range:

• Significant increases in low and mid-range torque

• Earlier turbo spool and improved throttle response

• Increased peak power potential

• Stronger acceleration and improved drivability

These benefits make the RB28 stroker combination ideal for street, drag, roll racing, and circuit applications using medium to large-frame turbochargers.

Crankshaft Specifications

• Application: Nissan RB25 & RB26

• Capacity: RB28 configuration

• Stroke: 77.7 mm

• Material: EN40B Billet Steel

• Fully Counterweighted

• Precision Nitrided

• Fully Balanced

• Designed for High Boost & High RPM Use

EN40B vs 4340 – Crankshaft Material Comparison

Summary:
4340 billet steel is a proven and reliable crankshaft material for many RB builds.
EN40B is a premium upgrade, selected for RB25 and RB26 engines operating at extreme power levels, sustained high RPM, and aggressive boost where fatigue resistance and long-term reliability are critical.

Engine build fitment

RB25|RB26. Match the selected dimensions, engine generation and rotating assembly specification before machining or assembly.

Installation and BBT workshop support

Measure journal and thrust clearances, check block clearance and balance the complete rotating assembly. Confirm the damper, crank trigger and flywheel arrangement with your engine builder.

Built by Boost & Tune is an authorised Spool Imports dealer and can assist with component selection, engine assembly and tuning requirements for your build.