RCM Subaru EJ# Main Bearing Journal Pinned & Line bore Engineering Process

RCM Subaru EJ# Line bore & Main Bearing Pinning Process

At RCM Engineering, precision, reliability, and performance are engineered into every stage of our Subaru EJ-series engine preparation. Developed from our Gobstopper program, our combined line bore and main bearing pinning process ensures absolute main tunnel alignment and long-term structural stability — essential for both high-performance road and motorsport applications.

Why the Process Matters

The Subaru EJ engine’s split-case design offers excellent strength-to-weight characteristics, but under high power, heat, and load, the main bearing housings can subtly shift. This microscopic movement leads to bearing wear, oil pressure loss, and crankshaft misalignment over time.

To counteract this, RCM developed a unique engineering process that combines precision line boring with bearing cap pinning — delivering permanent stability and exceptional crankshaft alignment, even in the most demanding conditions.

• Each main cap is precisely drilled and fitted with hardened steel dowel pins, securely locking it to its corresponding case half.

• This eliminates even the slightest cap movement under extreme stress and thermal cycling.

• The result is a rigid and repeatable main structure, maintaining perfect bearing geometry for the lifetime of the engine.

• The main bearing tunnel is digitally measured to identify any deviation from factory geometry.

• Using advanced CNC machining and line-honing equipment, the tunnel is corrected to within micron-level tolerances.

• This ensures perfect concentricity across all five main bearings, guaranteeing smooth crank rotation, consistent oil film, and balanced bearing load.

The RCM Advantage

Our combined line bore and pinning process delivers measurable benefits:

• Permanent main bearing stability, even under high torque or boost loads

• Improved oil pressure consistency and bearing life

• Reduced frictional losses and enhanced rotational balance

• Repeatable reliability for competition and endurance engines

Every machined block undergoes final inspection and digital measurement verification, ensuring RCM’s trademark standards of precision before assembly.

Proven in Motorsport, Perfected for the Road

From Time Attack winning engines to world-record-breaking road builds, RCM’s engineering processes have been proven time and time again under the harshest conditions. Whether you’re building a 400 bhp road car or a 900 bhp race engine, our line bore and bearing pinning process provides the precision foundation your EJ deserves.

RCM Engineering — Precision. Performance. Proven.