Brian Crower 4340 Billet Crankshaft – Nissan RB26DETT / RB25DET | 79mm Stroker | BC5239

This is a stroker crankshaft. The 79mm stroke increases displacement above stock on both RB26 (stock 73.7mm) and RB25 (stock 71.7mm). A complete rotating assembly specification — rod length, piston compression height, deck clearance — from an experienced RB engine builder is required before ordering.

This crank uses standard RB rod journal sizing (48mm). OEM RB26/RB25 rod bearings are not reused on a billet crank — source premium aftermarket rod bearings (King, ACL, Clevite) in 48mm for the correct clearance specification.

Brian Crower BC5239 4340 billet crankshaft for the Nissan RB26DETT and RB25DET. 79mm stroke, standard RB 48mm rod journals. Increases RB26 displacement to approximately 2,748cc. For Skyline GT-R and RB-powered high-power stroker builds. 70 lbs. Ships fast across Canada and the US.

79mm Stroker — RB26 and RB25 Displacement

The OEM Nissan RB26DETT uses a 73.7mm stroke with the 86mm bore for 2,568cc (2.6L) of displacement. Increasing stroke to 79mm with the same 86mm bore raises displacement to approximately 2,748cc (2.75L) — an 5.3mm stroke increase that adds meaningful torque across the RPM range and increases the engine’s fuelling and airflow demand proportionally. On the RB25DET (stock 71.7mm stroke, same 86mm bore), the 79mm stroke is an even greater increase, raising displacement similarly. The additional cubic centimetres allow the engine to generate more torque at lower boost levels compared to a stock-stroke combination targeting the same power output — reducing heat load on the turbocharger(s) and improving drivability at the same peak power target.

4340 Billet Construction

The BC5239 is machined from a single piece of 4340 chromoly steel billet bar stock. Billet construction provides a consistent, isotropic grain structure throughout the part with no seams, voids, or directional grain limitations. 4340 chromoly steel provides the tensile strength, toughness, and fatigue resistance required for the high rotational loads, torsional stress, and cylinder pressure forces of a high-power turbocharged inline-6 at serious power levels. The OEM RB26DETT crankshaft is a high-quality forged unit that holds up well at moderate power levels, but at 700–1,000+ hp on a built motor, billet quality removes the crankshaft from the list of potential failure points in the rotating assembly.

RB26DETT Platform — Skyline GT-R

The Nissan RB26DETT is the twin-turbocharged 2.6L inline-6 from the R32, R33, and R34 Skyline GT-R — one of the most celebrated and widely built JDM performance engines. The RB26’s iron block, forged crankshaft, and robust bottom end make it a capable platform for high-power builds, and a stroker crankshaft is a natural progression for GT-R builds targeting 800hp and above where the additional displacement provides a thermal and efficiency advantage over running a stock-stroke engine at extreme boost pressure.

RB25DET Platform

The Nissan RB25DET single-turbo 2.5L is used across the R33/R34 Skyline (non-GT-R), Stagea, Laurel, and other platforms. RB25-based builds are common in drift and time attack applications where the RB25 block is used with various head and forced induction configurations. The RB26 and RB25 share the same 86mm bore and crankshaft dimensions, making the BC5239 applicable to both platforms.

Required Rotating Assembly Components

Confirm with your engine builder before ordering:

• Connecting rods — must be specified for the 79mm stroke (correct center-to-center length for the increased stroke geometry) and 48mm RB rod journal big-end bore
• Pistons — must be specified for the correct compression height to achieve the desired deck clearance with the selected rod length and 79mm stroke
• Rod bearings — source premium aftermarket 48mm bearings (King, ACL, Clevite/Mahle); do not reuse OEM bearings on a billet crankshaft
• Main bearings — standard RB main bearing size; confirm with Brian Crower
• Balancing — balance the complete rotating assembly as a set after sourcing all components

Stroker crankshaft — complete rotating assembly spec required before ordering. Standard RB 48mm rod journals — source premium aftermarket rod bearings to correct clearance specification. Professional engine building and precision machining required. Balance complete rotating assembly before installation.

Specifications

• Brand: Brian Crower
• Part Number: BC5239
• Type: 4340 billet crankshaft
• Application: Nissan RB26DETT / RB25DET
• Stroke: 79mm (stock RB26: 73.7mm / stock RB25: 71.7mm)
• Rod Journal Diameter: 48mm (standard RB)
• Material: 4340 chromoly steel billet
• Weight: 70 lbs (shipping weight)