BC0138 – Brian Crower Mitsubishi 4B11 Evo X Stroker Kit – 98mm Stroke / ProH625+ Connecting Rods

In the relentless pursuit of volumetric efficiency and tractable power, engine displacement remains a foundational truth. For the Mitsubishi 4B11 engine powering the legendary Lancer Evolution X, the BC0138 Stroker Kit from Brian Crower represents the definitive volumetric solution for the serious builder. This isn’t merely a collection of parts; it is a cohesive engineering system designed to surgically increase displacement from 2.0L to a potent 2.3L, transforming the engine’s character from peaky turbo-four to a broad-shouldered torque monster. By integrating a meticulously engineered 98mm stroke crankshaft with the unparalleled strength of ProH625+ connecting rods and matched pistons, this kit delivers the robust, low-end grunt and high-RPM resilience required for dominant street, track, or strip performance. For those who understand that airflow is king and cylinder pressure is its throne, the BC0138 is the calculated upgrade that redefines the 4B11’s potential.

The Core of the Build: Material and Engineering Superiority

Every component in the BC0138 kit is subjected to a philosophy of excess strength and precision manufacturing. The foundation is a 4340 forged steel crankshaft, heat-treated and Tuftrided for exceptional core toughness and journal surface hardness. The critical stroke dimension is increased from the factory 86mm to a significant 98mm. This increase is not arbitrary; it is calculated to maximize displacement within the block’s architectural limits while maintaining optimal rod angularity and piston skirt guidance. Each counterweight is precisely balanced, and the crankshaft undergoes a rigorous micro-polishing process post-machining to eliminate stress risers and ensure flawless oil film retention at sustained high RPM.

Paired with this rotating assembly are Brian Crower’s flagship ProH625+ Connecting Rods. Fabricated from 4340 chromoly steel using a premium double-shear-cap design, these rods are the gold standard for high-stress applications. The “H625” designation refers to the material’s ultimate tensile strength—an extraordinary 625,000 psi—far exceeding the capabilities of standard 4340 or 5140 alloys. This immense strength allows for a more compact beam design, reducing reciprocating mass without sacrificing an iota of durability, a critical factor for high-revving, high-boost engines.

Precision-Matched Forged Pistons for Optimal Combustion

Completing the rotating assembly are 2618 forged aluminum pistons, CNC-machined to exacting specifications. These pistons are designed with the increased stroke and rod length in mind, featuring a tailored compression height and valve reliefs that are precision-cut to accommodate aggressive aftermarket camshafts. The use of 2618 alloy, as opposed to the softer 4032 alloy, is a deliberate choice for ultimate strength in severe duty and high-horsepower applications, particularly those involving high levels of forced induction. Each piston is weight-matched, and the kit includes high-performance piston pins and SpiroLox retainers, ensuring a complete, zero-compromise assembly.

• Substantial Displacement Increase: Elevates engine capacity from 2.0L to approximately 2.3L, generating significantly more torque and horsepower, especially in the low-to-mid RPM range.
• ProH625+ Rod Technology: Utilizes ultra-high-strength 4340 chromoly steel (625,000 psi UTS) for unprecedented resistance to bending and stretch under extreme cylinder pressure.
• Optimized Rotating Assembly: The combined 98mm stroke and ProH+ rod length is engineered for ideal rod-to-stroke ratio, minimizing parasitic friction and improving piston stability.
• Complete Kit Solution: Includes every necessary component—crank, rods, pistons, pins, rings, and bearings—ensuring perfect compatibility and simplifying the sourcing process.
• Foundation for Extreme Power: Provides the robust mechanical platform required to reliably support 800+ horsepower builds when combined with appropriate supporting modifications.

Vehicle Fitment: Precision Application for the 4B11 Platform

The BC0138 kit is engineered specifically for the Mitsubishi 4B11 engine family. Correct fitment is paramount for performance and reliability.

Primary Application:
• 2008-2015 Mitsubishi Lancer Evolution X (all trim levels, USDM and JDM)

Compatible With:
• Vehicles utilizing the 4B11 engine block. It is the builder’s responsibility to verify block casting and main cap architecture.
Important Notes: Installation of this stroker kit requires professional engine machining (boring/honing, decking, crankshaft balancing) and assembly by a qualified technician. Builder must select appropriate main and rod bearings based on final machining clearances. This kit significantly alters engine management parameters; mandatory supporting modifications include a professional tune, upgraded fuel system, and appropriate turbocharger sizing to fully exploit the increased displacement. Not legal for sale or use on pollution-controlled vehicles in California or other states adopting CARB regulations.

Technical Specifications & Part Data

Installation Philosophy and Final Build Considerations

Installing a stroker kit of this caliber is a commitment to a systems-level approach. The increased displacement and strength mandate complementary upgrades. The factory turbocharger will become a severe restriction; a larger turbocharger matched to the engine’s new airflow characteristics is essential. The fuel system—pump, injectors, and lines—must be scaled to feed the increased appetite. Most critically, the engine management system must be recalibrated by a tuner proficient in stroker engine dynamics to manage ignition timing, fuel delivery, and boost control accurately. The benefits, however, are transformative. The increase in displacement provides a profound improvement in off-boost response and mid-range torque, making the vehicle more driveable and reducing turbo lag. For a deeper technical exploration of stroker engine mechanics and their impact on performance, consider reading this resource on the fundamentals of stroker engine design.

The Brian Crower BC0138 Stroker Kit is not an entry-level modification. It is a strategic investment for the builder aiming for a definitive, no-excuses power plant. It provides the architectural advantage of increased displacement, wrapped in a package of ultimate material strength. For the Evolution X enthusiast dedicated to extracting the maximum potential from the 4B11 platform, this kit is the cornerstone of a truly legendary build.