ACL Bearings 5M1633H-.25 Race Series Main Bearing Set Oversize - 0.25mm

The ACL Bearings 5M1633H-.25 is a high-performance main bearing set designed for Nissan CA and CD series engines requiring 0.25mm oversize bearings. Part of ACL's Race Series lineup, these trimetal bearings are engineered for engine builders who demand superior quality and durability beyond standard OEM specifications.

Advanced Trimetal Construction:

• F780 bearing material featuring three layers: hardened steel backing, copper-lead intermediate layer, and high-strength overlay
• Reduced overlay thickness for improved fatigue resistance under high-load conditions
• Hardened steel backs improve bearing lining support and retention in the housing
• Trimetal composition significantly reduces friction and operating temperatures while enhancing lubrication

Race-Proven Design Features:

• Increased eccentricity compensates for bore distortion at high RPM and assists hydrodynamic oil film formation
• 3/4 groove design optimizes bearing load carrying surface area and oil flow to connecting rod bearings
• Increased crush for superior bearing retention during extreme conditions
• Elimination of flash plating on bearing backs improves heat transfer and housing grip
• Upper and lower bearing halves included for complete main journal coverage

Technical Specifications:

• Bearing Size: 0.25mm oversize
• Bearing Material: F780 tri-metal
• Overall Length: 20mm (0.787 inches)
• Maximum Shaft Size: 52.964mm (2.085 inches)
• Maximum Housing Bore: 56.667mm (2.231 inches)
• Vertical Oil Clearance Range: 0.036mm to 0.078mm
• Wall Thickness at Crown: 1.827mm (0.072 inches)

ACL bearings represent decades of Australian engineering excellence in precision bearing manufacturing. These Race Series bearings provide the perfect balance of strength and forgiveness, making them suitable for both high-performance street engines and competition applications where bearing loads are extreme but reliability is paramount.