ACL Race Series Main Bearing Set – Subaru EJ20 / EJ22 / EJ25 | STD | With Thrust (#5) | 5M8309HO/S2-STD

ACL 5M8309HO/S2-STD Race Series high performance main bearing set for Subaru EJ20, EJ22, and EJ25 engines. Full set of 5 main bearing shells, Standard (STD) bore, includes thrust bearing at journal position #5. ACL’s Race Series HO (High Output) design provides tighter oil clearances, harder tri-metal overlay, and higher load capacity than OEM-spec bearings — the standard choice for performance EJ engine builds. 0.8 lbs. Ships fast across Canada and the US.

ACL Race Series — High Output (HO)

ACL’s Race Series bearings are engineered for performance and high-output engine applications where OEM-specification bearings are inadequate for sustained high-load operation. The HO designation indicates ACL’s Race Series construction: a tri-metal overlay (copper-lead-tin) on a steel backing with tighter manufacturing tolerances than OEM replacement bearings. The harder overlay resists fatigue and wiping under high oil temperatures and elevated cylinder pressures typical of modified, high-boost, or high-revving EJ builds. ACL Race Series mains are the benchmark recommendation in the Subaru performance community for any EJ engine rebuild targeting reliability under modified power levels.

Full Main Set — 5 Bearings with Thrust at Position #5

The 5M8309HO/S2-STD is a complete main bearing set covering all five main journal positions on the EJ crankshaft. The `/S2` suffix indicates the set includes the thrust bearing at journal position #5 — the rear main journal, which is the thrust journal on the EJ engine controlling crankshaft end-play. Confirm your application requires thrust at position 5 before ordering. Sets without thrust bearing are available separately for applications where the thrust bearing is being sourced independently.

Standard (STD) Bore

This set is Standard bore — designed for EJ crankshafts at the OEM nominal main journal diameter with no regrinding or undersize machining of the journals. If your crankshaft journals have been reground to an undersized diameter, you will require the corresponding undersize bearing set, not this STD listing. Confirm journal diameter with your machinist using a micrometer measurement before ordering bearings. Do not order by the title description alone — always verify bore size against your actual measured journal diameter and target oil clearance.

EJ20 / EJ22 / EJ25 Application

ACL’s EJ main set covers all EJ-family engines sharing the same main journal dimensions: EJ20 (2.0L, used in WRX, STI, and numerous other Subaru applications), EJ22 (2.2L, Legacy and Impreza naturally aspirated), and EJ25 (2.5L, used in WRX, STI, Outback, Forester, and others). All EJ variants share common main journal geometry, making this a universal EJ main bearing set.

Professional Engine Building Required

ACL Race Series bearings are a precision performance component intended for use during a full engine rebuild. Correct installation requires thorough cleaning of all bearing journals and housings, precise oil clearance measurement using Plastigage or micrometer comparison, torquing to the correct main cap specification, and proper pre-lubrication before first start. Incorrect installation, contaminated journals, or improper oil clearance will result in premature bearing failure and potential catastrophic engine damage. Professional engine building by an experienced machinist is strongly recommended.

Standard (STD) bore — verify crankshaft journal diameter before ordering. Not compatible with reground or undersized journals. Professional engine building required. For EJ20, EJ22, and EJ25 applications only.

Specifications

• Brand: ACL
• Part Number: 5M8309HO/S2-STD
• Series: Race Series (High Output)
• Type: Main bearing set
• Quantity: 5 bearings (complete main set)
• Thrust: Included — position #5
• Bore Size: Standard (STD)
• Application: Subaru EJ20 / EJ22 / EJ25 — all variants
• Weight: 0.8 lbs