ACL 8B1578H-STD Race Series Rod Bearing Set STD BMW N63/S63 4.4L V8

Vehicle Fitment

• 2009-2015 BMW 750i / 750Li F01/F02 (N63B44A, 4.4L Twin-Turbo V8)
• 2013-2016 BMW 550i / 550i GT F10/F07 (N63B44B, 4.4L Twin-Turbo V8)
• 2010-2018 BMW X5 xDrive50i E70/F15 (N63B44A/B, 4.4L Twin-Turbo V8)
• 2012-2018 BMW X6 xDrive50i E71/F16 (N63B44A/B, 4.4L Twin-Turbo V8)
• 2016-2023 BMW 750i / 750Li G11/G12 (N63B44O2 / N63M20A, 4.4L Twin-Turbo V8)
• 2012-2017 BMW M5 F10 (S63B44B, 4.4L Twin-Turbo V8)
• 2018-2023 BMW M5 F90 (S63B44T0, 4.4L Twin-Turbo V8)
• 2012-2018 BMW M6 Coupe / Convertible / Gran Coupe F12/F13/F06 (S63B44B, 4.4L Twin-Turbo V8)
• 2015-2019 BMW X5M F85 (S63B44T0, 4.4L Twin-Turbo V8)
• 2015-2019 BMW X6M F86 (S63B44T0, 4.4L Twin-Turbo V8)
• 2020-2023 BMW M8 Coupe / Convertible / Gran Coupe F91/F92/F93 (S63B44T0, 4.4L Twin-Turbo V8)
• 2015-2023 BMW M5 CS / Competition / GTS variants (S63R, 4.4L Twin-Turbo V8)

Note: Fitment confirmed through ACL's official Race Series Application Guide (2023), Summit Racing, FCP Engineering, and Xtune.eu. This bearing set applies to all N63B44 and S63B44 engine variants produced from March 2011 onward. Always measure crankshaft journal diameters before ordering to confirm STD size is correct - if journals have been machined undersize, order the appropriate -025 (.25mm undersize) variant instead. Sold as a set of 8 bearing shells (complete set for all 8 connecting rods on the V8). Professional engine builder installation is required.

Features

• ACL Race Series tri-metal construction - high-strength steel back, copper-lead alloy lining, and lead-bronze overlay for superior fatigue resistance, load capacity, and friction reduction vs. standard OEM bearings
• No flash plating on the back of the shells - eliminates the risk of overlay migration under high load and heat, improving heat transfer and maximizing bearing-to-housing contact
• Hardened steel backs on all rod bearings - provides superior support for the bearing lining and assists with bearing retention in the connecting rod housing bore
• Increased crush for improved bearing retention - ensures the bearing shells remain firmly seated in the connecting rod bore under high-RPM and high-load conditions
• Increased eccentricity to compensate for bore distortion - improves shape adaptation under operating load for more consistent oil film across the bearing surface
• Tight, consistent wall tolerances - enables precise and repeatable oil clearance measurement and control during engine assembly
• Enlarged ID chamfers on bearing edges - accommodates the large fillet radius on performance and aftermarket crankshafts
• 2 locating notches per shell - ensures precise alignment and secure retention in both connecting rod cap and beam halves
• Identical halves - both upper and lower shells are interchangeable, simplifying inventory and assembly
• Motorsport-proven material specification - ACL Race Series technology traces its origins to Formula 1 (Brabham), Australian Supercars, NASCAR, NHRA, and IHRA competition

Specifications

• Part Number: 8B1578H-STD
• Brand: ACL Race Series Performance Engine Bearings
• Bearing Type: Connecting Rod (Big End) Bearings
• Size: STD (Standard - for use on standard, unmachined crankshaft rod journals)
• Bearing Material: F781 Tri-Metal (Steel back / Copper-lead lining / Lead-bronze overlay)
• Quantity: Set of 8 shells (complete set for 8-cylinder V8)
• Half Type: Identical halves (upper and lower shells are the same)
• Locating Notches: 2 per shell
• Crankshaft Rod Journal Tunnel (Housing Bore): 57.600-57.616mm
• Standard Shaft Journal Diameter: 53.971-53.990mm
• Vertical Oil Clearance Range: 0.055-0.103mm (0.0022"-0.0041")
• Max Wall Thickness at Crown: 1.794mm (0.0707")
• Max Overall Bearing Length: 15mm (0.5906")
• Compatible Engine Codes: N63B44 (all variants), S63B44 (all variants), S63R
• Engine Application: From March 2011 onward

Included Components

• 8x ACL Race Series Connecting Rod Bearing Shells (complete set for one V8 engine)
• Note: ARP rod bolts, assembly lube, and other fasteners are NOT included and must be sourced separately

Product Description

The ACL 8B1578H-STD is a full set of Race Series tri-metal connecting rod bearings for the BMW N63B44 and S63B44 4.4L twin-turbo V8 engine family, covering all variants produced from March 2011 onward. This includes naturally performance-oriented applications like the M5 (F10/F90), M6 (F12/F13/F06), X5M (F85), X6M (F86), and M8 (F91/F92/F93), as well as the high-output S63R variant found in M5 CS and GTS models, and N63B44-equipped luxury models including the 750i, 550i, and X5/X6 xDrive50i. The set ships as 8 identical bearing shells - one for each of the V8's connecting rod journals - with interchangeable upper and lower halves for simplified assembly.

ACL Race Series bearings use a tri-metal construction consisting of a hardened steel back for structural rigidity, a copper-lead alloy intermediate lining for thermal conductivity and load distribution, and a lead-bronze overlay with high fatigue resistance for direct contact with the crankshaft journal. Unlike OEM bearings, ACL Race Series shells carry no cosmetic tin flash plating on the back face - a deliberate design decision that eliminates the risk of overlay material migrating under high heat and load, which can create high spots on the back of the shell and distort the bearing seat. This also improves heat transfer away from the bearing surface into the connecting rod housing. Increased bearing crush ensures the shells remain firmly seated under the high-RPM, high-load conditions common in modified N63/S63 builds, and tight wall tolerances allow engine builders to achieve consistent and repeatable oil clearances across all eight journals during assembly.

The 8B1578H-STD is sized for standard (unmachined) crankshaft rod journal diameters of 53.971-53.990mm. Before ordering, engine builders must measure the actual crankshaft journal diameters with a micrometer - if any journals have been machined undersize during reconditioning, the appropriate undersize variant (8B1578H-25 for .25mm undersize journals) must be used instead. ACL also produces an HX-STD variant (8B1578HX-STD) with 0.013mm thinner walls providing an additional 0.025mm nominal oil clearance for builders targeting looser clearances in high-power applications. Installation must be performed by a qualified engine builder using precision measuring tools, clean assembly lubricant, and torqued rod bolts per application specifications.