ACL 4B1946H-.25 Race Rod Bearing Set +0.25mm Honda B16A B18A B18B B20B Integra

Vehicle Fitment

• 1989-2001 Honda Civic / CRX / Del Sol - B16A, B16A2, B16A3 variants (1.6L DOHC 16v VTEC)
• 1992-1993 Acura Integra GS-R (B17A1, 1.7L DOHC 16v VTEC)
• 1990-1993 Acura Integra GS/LS/RS (B18A1, 1.8L DOHC non-VTEC)
• 1994-2001 Acura Integra GS/LS/RS (B18B1/B18B2, 1.8L DOHC non-VTEC)
• 1997-2001 Honda CR-V (B20B / B20Z, 2.0L DOHC non-VTEC)
• Various JDM Honda Accord, Odyssey, Torneo - F18B, F20B (1.8L/2.0L SOHC VTEC)
• Honda B20A SOHC variants (1.958L SOHC)

Fitment Notes

• The .25 suffix designates this as the +0.25mm oversize bearing set - intended for use when the crankshaft rod journals have been ground 0.25mm undersize during a rebuild. The thicker wall restores correct running oil clearance on a more significantly reground crankshaft.
• Do NOT use on a stock, unground crankshaft. For standard journal diameter, use 4B1946H-STD. For crankpins ground 0.025mm undersize, use 4B1946H-.025.
• Always measure crankshaft rod journal diameter with a micrometer before selecting bearing size. Confirm actual clearance with Plastigage or a dial bore gauge after assembly.
• This bearing covers the broad Honda B-series (non-VTEC and B16A VTEC) and F-series SOHC family - all sharing identical crankpin journal dimensions. Note that the VTEC B18C series (B18C1, B18C5 etc.) uses a different bearing set (4B1925H).
• Sold as a complete set of 8 bearing shells - sufficient for one full 4-cylinder engine build.
• UPC: 9315726277577

Features

• Tri-metal construction: copper-lead alloy lining bonded over a hardened steel backing, with a high-strength overlay plate - engineered for the high-RPM and forced-induction demands of built Honda B-series and F-series engines.
• Hardened steel backing on all rod bearings improves structural support of the bearing lining and maintains crush under high sustained loads and temperatures.
• High-strength overlay plate with reduced thickness provides improved fatigue resistance compared to OEM-spec bearings - critical in boosted or high-revving B-series builds at elevated power levels.
• 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: 4B1946H-.25
• Product Line: ACL Race Series
• Application: Connecting Rod Bearings
• Engine Compatibility: Honda/Acura B16A variants (1595cc); B17A1 (1678cc); B18A, B18A1, B18B1, B18B2 (1834cc); B20A SOHC, B20B, B20Z (1958/1972cc); F18B, F20B (1850/1997cc SOHC VTEC)
• Crankshaft Size: +0.25mm Oversize (for crankpins ground 0.25mm undersize)
• Shaft (Crankpin) Diameter: 44.730-44.750mm (1.7610-1.7618 in)
• Tunnel (Housing Bore): 48.000-48.024mm (1.8898-1.8907 in)
• Maximum Wall Thickness at Crown: approx. 1.629mm (0.0641 in)
• Maximum Overall Length: 19.50mm (0.768 in)
• Bearing Material: Tri-Metal Copper-Lead Alloy / Hardened Steel Backing
• Quantity: Set of 8 Shells (complete engine set)
• UPC: 9315726277577

Included Components

• 8x Race Series Connecting Rod Bearing Shells - +0.25mm Oversize

Product Description

The ACL Race Series 4B1946H-.25 connecting rod bearing set is the +0.25mm oversize option for Honda/Acura's broad B-series and F-series inline-4 engine family - covering the B16A, B17A1, B18A1, B18B1, B20B, B20Z, and related SOHC F-series engines found in the Civic, CRX, Del Sol, Acura Integra (non-VTEC and B17), CR-V, and various JDM platforms. This oversize set is selected when the crankshaft rod journals have been ground 0.25mm undersize to address wear or scoring during a rebuild, restoring correct oil clearance on the reground crank.

All engines listed share identical crankpin journal dimensions, making this a single versatile set for rebuilds across the B/F-series family at the +0.25mm oversize. Note that the B18C VTEC engines (B18C1, B18C5) use a different bearing with a separate part number (4B1925H). Built on ACL's Race Series tri-metal platform, these bearings deliver superior fatigue resistance and oil film stability over OEM Honda shells. Always verify crankshaft journal diameter with precision measurement and confirm clearances at assembly before final torque. Sold as a complete set of 8 shells for one engine.