ACL 5M8309H-.025 Race Main Bearing Set for Subaru EJ20/EJ22/EJ25

Vehicle Fitment

• Subaru 4-cyl Boxer: EJ18, EJ20, EJ22, EJ25 (thrust in #5 position)
• Includes turbo, naturally aspirated, and twin-turbo variants where applicable

Features

• High-performance Race Series tri-metal construction
• Undersize (-.025 mm) to suit machined crankshafts
• Hardened steel backing for increased load support
• Increased eccentricity to improve hydrodynamic oil film
• 3/4-groove upper mains for optimized load area and oil flow
• No flash plating on back - better heat transfer to housing
• Tight, consistent wall tolerances for precise clearances
• Enlarged chamfers to accommodate performance crank fillets

Specifications

• Part Number: 5M8309H-.025
• Size: -0.025 mm (undersize)
• Oil Clearance: Standard
• Shaft Diameter (journal): ~59.984 - 60.000 mm
• Tunnel (housing) Diameter: ~64.000 - 64.020 mm
• Max Wall Thickness at Crown: ~2.005 mm
• Bearing Width: ~19.0 mm
• Half Type: Identical halves

Included Components

• 5x main bearing shells (complete set for one engine)

Product Description

The ACL 5M8309H-.025 is a precision-engineered main bearing set from ACL's Race Series, specifically designed for Subaru EJ-series engines. With a -0.025 mm undersize specification, it suits crankshafts that have been ground, ensuring correct clearance for high-performance builds.

Made with tri-metal construction, these bearings deliver excellent durability under high RPM and stress. The hardened steel backing enhances load support, while the increased eccentricity helps maintain a stable oil film during high-speed operation. The 3/4-groove design allows optimized load-carrying surface area and efficient oil distribution.

Ideal for performance engine builders working on naturally aspirated or turbocharged Subaru EJ20, EJ22, or EJ25 engines (and other compatible EJ variants), these bearings provide reliable clearance control and long-lasting performance in demanding applications.