Mastering the Subaru EJ Engine Build: Tips for Reliability and Performance

Introduction to Building a Subaru EJ Engine for Performance and Reliability

Subaru's EJ engine series, known for its potential but also its proneness to failure, requires a careful approach to achieve both reliability and performance. This article delves into the intricacies of building a Subaru EJ engine, specifically focusing on a stroker EJ205 build that aims to blend the torque of the EJ257 with the rev-happy nature of the 2-liter WRX engine.

Key Considerations in EJ Engine Builds

To ensure the engine breathes properly, which is crucial for generating power, considerable attention must go into modifying the cylinder head. CNC porting of the EJ205 heads helps improve airflow by smoothing sharp edges and optimizing flow paths. Valve jobs using CNC machines, as opposed to traditional methods, create a smoother transition from the combustion chamber to the port, significantly boosting power.

Upgraded Components for Enhanced Flow and Reliability

• Valves: Supertech intake and exhaust valves, made from nitrided stainless steel and Inconel respectively, are chosen for their durability and ability to improve flow. The exhaust valve's straight contour aids in smoother flow into the exhaust port, while the intake valve's tulip profile facilitates better airflow into the combustion chamber.

• Camshafts: A Kelford 199K series camshaft with moderate duration and high lift is selected to balance performance and streetability, avoiding overly narrow power bands and poor low-RPM characteristics.

• Valve Springs: Kelford beehive valve springs are used for their ability to compress more, reduce valve float, and handle the aggressive valve motion introduced by the high-lift camshaft.

Building a Strong Foundation: Engine Block Modifications

Modifying the engine case is essential for handling increased power. The case is reinforced through a closed-deck conversion by Outfront Motorsports, significantly reducing flex and bearing wear. Align boring and precise machining ensure the integrity of bearing bores and cylinder walls, countering common Subaru engine rebuild issues.

The Role of Connecting Rods and Pistons in Engine Dynamics

Longer connecting rods are employed to slow piston acceleration, reducing stress on components and enhancing the engine's revving characteristics. JE pistons, designed with a focus on lightweight and strength, complement the longer rods and contribute to the engine's free-revving feel.

Crankshaft, Oil System, and Harmonic Balancer: Ensuring Durability and Efficiency

An Eagle crankshaft with a longer stroke is selected to increase displacement without compromising the engine's ability to rev. The oil system is upgraded with a larger pump and improved oil pan, windage tray, and pickup from Killer B Motorsport to ensure adequate lubrication and oil control. A Fluidampr harmonic balancer is added to reduce vibrations and potentially increase power.

Final Touches for Reliability and Performance

King XP bearings are chosen for their durability and heat conductivity. The entire engine, including the crankshaft, rods, pistons, and bearings, undergoes WPC treatment and cryogenic processing to enhance wear resistance and fatigue strength.

Conclusion

Building a Subaru EJ engine that is both powerful and reliable requires meticulous attention to detail, from airflow optimization to strengthening the engine block and carefully selecting upgraded components. By following these guidelines, enthusiasts can enjoy the benefits of a high-performing Subaru engine that stands up to the rigors of both street and track use.

For more information and detailed insights into building Subaru engines, watch the full video here.