ACL 4B1906HX-STD Race Rod Bearing Set STD +0.001" Honda K20A3 F23A Civic RSX

Vehicle Fitment

• 2002-2006 Acura RSX Base (K20A3, 2.0L DOHC 16v i-VTEC)
• 2002-2005 Honda Civic Si / EP3 (K20A3, 2.0L DOHC 16v i-VTEC)
• 1998-2002 Honda Accord - DX, LX, EX (F23A1/A4/A5/A7, 2.3L SOHC 16v VTEC)
• 1998-1999 Acura CL 2.3 (F23A1, 2.3L SOHC 16v VTEC)
• 1998 Honda Odyssey (F23A, 2.3L SOHC VTEC)
• 1999 Isuzu Oasis (F23A, 2.3L SOHC VTEC)
• Various Euro-market Honda Accord, CR-V, FR-V, Prelude with K20A3 or F23A/F23Z engine codes

Fitment Notes

• The HX designation indicates extra oil clearance: the bearing wall is approximately 0.013mm thinner per shell compared to the standard 4B1906H-STD set, providing approximately 0.025mm (0.001") of additional running clearance at standard crankshaft journal diameter - without any crankshaft grinding.
• Recommended for high-performance, high-RPM, or forced-induction K20A3 and F23-series builds where slightly increased oil film thickness is desired for improved bearing protection under elevated loads and temperatures.
• For standard oil clearance at stock journal diameter, use 4B1906H-STD. For reground crankshafts, use the appropriate oversize H set: 4B1906H-.025, 4B1906H-.25, or 4B1906H-.50.
• Note: The higher-performance K20A2 and K20Z1 engines use a different bearing set (4B1972HX-STD) with larger crankpin journals. Verify your specific engine code before ordering.
• Always confirm actual running clearance with Plastigage or a dial bore gauge after assembly - do not rely solely on bearing size designation.
• Sold as a complete set of 8 bearing shells - sufficient for one full 4-cylinder engine build.

Features

• Tri-metal construction: copper-lead alloy lining bonded over a hardened steel backing, with a high-strength overlay plate - engineered for the high-revving, VTEC-enabled demands of built K20 and F-series Honda engines.
• HX extra-clearance wall thickness provides approximately 0.025mm (0.001") of additional oil clearance versus the H-STD set, increasing oil film volume between the crankpin and bearing surface for improved lubrication under extreme load.
• Hardened steel backing on all rod bearings improves structural support of the bearing lining and maintains crush under high sustained loads.
• High-strength overlay plate with reduced thickness provides improved fatigue resistance compared to OEM-spec bearings - important in high-RPM naturally aspirated and forced-induction K20A3 applications.
• Increased bearing crush and tighter wall tolerances ensure consistent, secure seating in the connecting rod housing bore, reducing the risk of bearing spin.
• Enlarged ID chamfers on bearing edges accommodate the larger fillet radii found on performance and aftermarket Honda crankshafts.
• 3/4-groove design optimizes oil supply to the rod journal and maximizes load-carrying surface area across the bearing face.
• Elimination of flash plating on bearing backs improves heat transfer and maximizes grip between the bearing shell and the rod housing bore.
• Increased eccentricity compensates for bore distortion at high RPM and assists in the formation of a stable hydrodynamic oil film under load.

Specifications

• Part Number: 4B1906HX-STD
• Product Line: ACL Race Series
• Application: Connecting Rod Bearings
• Engine Compatibility: Honda K20A3 (1998cc DOHC 16v i-VTEC); Honda F23A1, F23A4, F23A5, F23A7, F23Z2, F23Z4 (2254cc SOHC 16v VTEC)
• Crankshaft Size: Standard (STD - Unground)
• Oil Clearance Designation: HX - Extra +0.025mm (+0.001") clearance vs. H-STD
• Shaft (Crankpin) Diameter: 44.976-45.001mm (1.7707-1.7717 in)
• Tunnel (Housing Bore): 48.006-48.017mm (1.8899-1.8904 in)
• Maximum Wall Thickness at Crown: approx. 1.489mm (0.0586 in)
• Maximum Overall Length: 15.50mm (0.610 in)
• Bearing Material: Tri-Metal Copper-Lead Alloy / Hardened Steel Backing
• Quantity: Set of 8 Shells (complete engine set)

Included Components

• 8x Race Series Connecting Rod Bearing Shells - Standard Size, Extra Oil Clearance (HX)

Product Description

The ACL Race Series 4B1906HX-STD connecting rod bearing set is the extra-clearance performance option for the Honda K20A3 and F23A/F23Z engine families - the 2.0L DOHC K20A3 found in the Acura RSX Base and Honda Civic Si EP3, and the 2.3L SOHC F23 family found in the Honda Accord and related Acura CL. Sharing the same standard crankpin journal diameter as the 4B1906H-STD, the HX variant uses a slightly thinner wall (~0.013mm per shell) to deliver approximately 0.025mm (0.001") of additional running oil clearance without any crankshaft modification. This increased clearance supports a thicker hydrodynamic oil film - a meaningful advantage in high-RPM naturally aspirated builds or any forced-induction K20A3 application where a more liberal oil clearance specification is preferred.

Built on ACL's Race Series tri-metal platform, these bearings deliver superior fatigue resistance, bearing retention, and oil film stability compared to OEM Honda shells. For the performance-focused K20A2 and K20Z1 engines, use the 4B1972HX-STD set instead. Always confirm actual running clearance at assembly. Sold as a complete set of 8 shells for one engine.