ACL 5M8309HOS5-STD +0.005" Oversize Main Bearing Set for Subaru EJ Engines

Vehicle Fitment

• Subaru 4-cyl Flat-4: EJ18, EJ20, EJ22, EJ25 (thrust in #5 position)
• Includes naturally aspirated and turbo versions (Impreza, Forester, Legacy, Outback, etc.)

Features

• Race-series tri-metal construction for superior strength and fatigue resistance
• +0.005" (≈ 0.127 mm) oversize housing spec ("OS5") for blocks bored out
• Standard oil clearance to maintain reliable lubrication
• Increased eccentricity to help maintain stable oil film under high RPM
• ¾-groove design optimizes load surface and oil flow
• No flash plating on back to maximize heat transfer to housing
• High crush design improves bearing retention in the block
• Enlarged ID chamfers to accommodate performance crank fillets

Specifications

• Part Number: 5M8309HOS5-STD
• Bearing Size: Standard (STD)
• Housing Oversize: +0.005" (OS5)
• Oil Clearance: Standard
• Half Type: Identical upper/lower shells
• Material: Tri-metal (steel backing, copper-lead intermediate, lead/tin overlay)
• Max Shaft Size (STD): ~60.00 mm
• Max Tunnel (Housing) Size: ~64.147 mm
• Max Wall Thickness at Crown: ~2.069 mm
• Max Overall Shell Length: ~22.92 mm

Included Components

• 5x main bearing shells (full set for one Subaru EJ-series engine)

Product Description

The ACL 5M8309HOS5-STD is a performance main bearing set from ACL's Race Series, specifically made for Subaru EJ-series engines. Its +0.005" oversize ("OS5") housing spec makes it ideal for engine blocks that have been bored or line-honed, giving a precise fit where standard-size bearings may not seat properly.

Featuring tri-metal construction, these bearings offer high strength, optimal load resistance, and excellent fatigue characteristics. Their ¾-grooved design improves oil distribution and helps maintain a stable lubrication film even in high-RPM, high-stress environments. The increased eccentricity further supports oil film formation under demanding conditions.

This bearing set is well-suited for engine builders working on tuned or rebuilt Subaru EJ motors - whether turbocharged or naturally aspirated. If your block has been machined oversize, this OS5 set ensures you maintain proper bearing clearance, reliability, and longevity in your build.