ACL BMW N63B44/S63B44 4.4L V8 .025mm Oversized Main Bearings

SKU: 5M1573H-.025 / UPC: 9315726470190

ACL BMW N63B44/S63B44 4.4L V8 .025mm Oversized Main Bearings

The ACL Race Series main bearings deliver precise crankshaft support and consistent oil flow in high-output applications. These .025mm oversized bearings accommodate machined crankshaft journals, ensuring tight tolerances and reduced vibration for smoother operation across the RPM range. Built with ACL’s F780 material for enhanced fatigue strength and corrosion resistance, they feature a 3/4 grooved design on select shells to direct oil efficiently to connecting rod bearings while maintaining full load-carrying surfaces on thrust positions. Ideal for rebuilds or performance upgrades on N63B44 and S63B44 engines, this set provides the dependable foundation needed for track days or daily driving, outperforming standard replacements through advanced metallurgy and exacting tolerances that hold up under boosted pressures and elevated temperatures.

What’s Included in Your Purchase

• Complete Main Bearing Set: 5 pairs of upper and lower bearings (10 shells total) covering all main journal positions (1-5), including thrust bearings at positions 2 and 4.
• Part Number: 5M1573H-.025
• UPC: 9315726470190
• Oversize Specification: .025mm (0.001 inch) – Designed for crankshafts machined to 64.971–64.990mm shaft diameter and 70.000–70.019mm tunnel diameter.
• Material: F780 tri-metal construction with polymer overlay for low-friction startup and high-load durability.
• Bearing Dimensions:
• Maximum Wall Thickness: 2.500mm
• Maximum Length: 22.25mm (non-flanged shells)
• Product Weight: 0.43 kg (0.95 lbs)
• Shipping Details: Packaged in a compact box measuring 3 x 3 x 2 inches; total shipping weight 1 lb.

Vehicle Fitment

These bearings fit BMW models equipped with the N63B44 (4395cc V8 Twin Turbo, introduced 2008) or S63B44 (4395cc V8 Twin Turbo, introduced 2009) engines. Compatible with both original and TU (Technical Update) variants. Verify your engine code for exact match.

This ACL set installs directly without modifications, supporting oil clearances from 0.001–0.003 inches for balanced lubrication in stock or modified setups. Pair with ACL rod bearings for a full bottom-end refresh.