ACL 4B1630H-.25 Race Rod Bearing Set +0.25mm Nissan CA18DET CA16 CA18 CA20

Vehicle Fitment

• Nissan CA16 - 1.6L (1598cc) SOHC 8v Inline-4 (Naturally Aspirated)
• Nissan CA16DE - 1.6L (1598cc) DOHC 16v Inline-4 (Naturally Aspirated)
• Nissan CA18 / CA18E - 1.8L (1809cc) SOHC 8v Inline-4 (Naturally Aspirated)
• Nissan CA18DE - 1.8L (1809cc) DOHC 16v Inline-4 (Naturally Aspirated)
• Nissan CA18ET - 1.8L (1809cc) SOHC 8v Inline-4 Turbo
• Nissan CA18DET - 1.8L (1809cc) DOHC 16v Inline-4 Twin-Cam Turbo
• Nissan CA20 / CA20E - 2.0L (1974cc) SOHC Inline-4 (Naturally Aspirated)
• Nissan CD17 - 1.7L Inline-4 Diesel

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 4B1630H-STD. For crankpins ground 0.025mm undersize, use 4B1630H-.025. For crankpins ground 0.50mm undersize, use 4B1630H-.50.
• 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.
• 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-RPM and forced-induction demands of built CA-series Nissan engines, particularly the CA18DET.
• 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 turbocharged CA18ET and CA18DET builds at elevated boost pressures.
• 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 CA-series 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: 4B1630H-.25
• Product Line: ACL Race Series
• Application: Connecting Rod Bearings
• Engine Compatibility: Nissan CA16, CA16DE, CA18, CA18E, CA18DE, CA18ET, CA18DET, CA20, CA20E, CD17
• Crankshaft Size: +0.25mm Oversize (for crankpins ground 0.25mm undersize)
• Shaft (Crankpin) Diameter: 44.961-44.974mm (1.7701-1.7706 in)
• Tunnel (Housing Bore): 48.000-48.013mm (1.8898-1.8903 in)
• Maximum Wall Thickness at Crown: 1.505mm (0.0593 in)
• Maximum Overall Length: 18.6mm (0.732 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 - +0.25mm Oversize

Product Description

The ACL Race Series 4B1630H-.25 connecting rod bearing set is the +0.25mm oversize option for Nissan's CA-series inline-4 engine family - covering the CA16, CA18, CA18DET, CA20, and related variants that powered some of the most iconic JDM and export performance cars of the 1980s and early 1990s, including the Silvia S12 and S13, the 180SX, and the European 200SX. This oversize set is selected when the crankshaft rod journals have been ground 0.25mm undersize to address surface wear, scoring, or out-of-round conditions during a rebuild. The thicker-walled bearing shell compensates precisely for the reduced crankpin diameter, restoring correct oil clearance on the reground crank.

The CA18DET in particular remains one of the most rebuilt and modified engines in Japanese performance history, and ACL Race Series bearings are a standard specification for serious CA18DET rebuilds at any power level. Built on ACL's proven tri-metal platform with superior fatigue resistance, crush, and oil film stability compared to OEM shells. Always verify crankshaft journal diameter with precision measuring equipment and confirm clearances at assembly before final torque. Sold as a complete set of 8 shells for one engine.