3.6L 12v - M64

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3.6L 12v - M64

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ACL trimetal connecting rod bearings Porsche 993 M64 3.6 3.8

New product

Set of 12 trimetal connecting rod half-bearings for Porsche 911 (993) M64.

  • Brand and treatment: ACL Race
  • Compatibility: 911 (993) Carrera 3.6 and 3.8, Carrera RS, Turbo, GT2
  • Engine codes: M 64.05 to M 64.08, M 64.20 to M 64.24, M 64.60
  • Available sizes: standard to +0.25 mm, increased-clearance version (HX)

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103,33 € tax incl.

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108,77 € tax incl.

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  • The Porsche 993 M64 flat-six engines

    The M64 of the Porsche 911 type 993 is the last air-cooled flat-six: 3.6 litres in the Carrera (M 64.05 to M 64.08, M 64.21 to M 64.24) and in the turbocharged Turbo and GT2 (M 64.60, M 64.60R, M 64.60RS), 3.8 litres in the 3.8 Carrera, Carrera 4 and Carrera RS (M 64.05S, M 64.06S, M 64.20, M 64.21S). ACL lists the same bearing set for all these engines: a single set covers the family.

    From the factory, this engine is fitted with standard production connecting rod bearings, sized for the loads of the original engine: as soon as power, engine speed or boost pressure increase, they reach their limits.

    Trimetal connecting rod bearings

    A trimetal bearing stacks three layers: a steel back, a copper-lead intermediate layer with high load capacity and an anti-friction running surface that protects the journal. The complete set contains 12 half shells, six pairs for a six-cylinder engine.

    Technical specifications

    Fitment dimensions common to all references
    ACL bearings
    Crankpin Ø 54.971 / 54.990 mm
    Housing bore Ø 58.000 / 58.019 mm
    Width 14.8 mm
    ReferenceBrand and treatmentSizeWall thickness (mm)
    6B2473H-STDACL Race - UntreatedStandard1.499
    6B2473HX-STDACL Race - UntreatedStd, increased clearance (HX)1.486
    6B2473H-.025ACL Race - Untreated+0.0251.512
    6B2473H-.25ACL Race - Untreated+0.251.624

    Running clearance

    The running clearance is the gap between the bearing and the journal where the oil film flows.

    In operation, the crankshaft journal does not rub against the bearing: it rides on this oil film, which carries the load. Clearance sets the thickness of this film: too tight, oil flows poorly, temperature rises and the risk of seizure increases; too loose, oil escapes, the film loses load-carrying capacity and oil pressure drops. The right clearance is the balance between adequate lubrication and a well-maintained oil film.

    Size / gradeWhen to choose itACL Race Series
    Standard (STD)Standard journal, not reground0.057 to 0.068 mm
    Increased clearance (HX)Wider clearance: high oil flow, high rpm0.082 to 0.093 mm
    +0.025 mmPolished journal0.057 to 0.068 mm
    +0.25 mmJournal reground to 0.25 mm0.057 to 0.068 mm

    Checking on assembly: lay a calibrated strip (Plastigauge) on the journal, torque the rod cap to spec, then compare the crushed strip against the gauge to read the clearance.

    Plastigauge

    Order the Plastigauge →

    Technical guide

    The ACL rod bearings shown here are trimetal bearings, designed for engine building and racing. Compared with an original bearing, they handle far higher loads: they cope with increased power, high rpm or the addition of a turbo or supercharger, where a standard bearing quickly reaches its limit.

    The brand

    ACL Bearing CompanyACL Bearing Company, an Australian manufacturer of high-performance engine bearings since 1949, offers with its Race Series precise trimetal bearings, available in many sizes and proven on built engines worldwide.

    Vehicle compatibility

    This connecting rod bearing set fits the M64 flat-six engines of the following Porsche 911 (993) models:

    BrandModel (chassis)Engine codePowerYears
    PORSCHE911 (993) 3.6 CarreraM 64.07, M 64.08, M 64.05, M 64.06272 hp1993–1995
    PORSCHE911 Convertible (993) 3.6 CarreraM 64.07, M 64.08, M 64.05, M 64.06272 hp1994–1995
    PORSCHE911 (993) 3.6 Carrera 4M 64.07, M 64.05272 hp1994–1995
    PORSCHE911 Convertible (993) 3.6 Carrera 4M 64.07, M 64.05272 hp1994–1995
    PORSCHE911 (993) 3.6 CarreraM 64.24, M 64.21, M 64.22, M 64.23286 hp1995–1997
    PORSCHE911 Convertible (993) 3.6 CarreraM 64.24, M 64.21, M 64.22, M 64.23286 hp1995–1997
    PORSCHE911 Targa (993) 3.6 CarreraM 64.24, M 64.21, M 64.22, M 64.23286 hp1995–1997
    PORSCHE911 (993) 3.6 Carrera 4M 64.21, M 64.23286 hp1995–1997
    PORSCHE911 Convertible (993) 3.6 Carrera 4M 64.21, M 64.23286 hp1995–1997
    PORSCHE911 (993) 3.8 CarreraM 64.05S, M 64.06S286 hp1995–1997
    PORSCHE911 Convertible (993) 3.8 CarreraM 64.05S, M 64.06S286 hp1995–1997
    PORSCHE911 (993) 3.8 Carrera 4M 64.05S, M 64.06S286 hp1995–1997
    PORSCHE911 Convertible (993) 3.8 Carrera 4M 64.05S, M 64.06S286 hp1995–1997
    PORSCHE911 (993) 3.8 CarreraM 64.21S301 hp1995–1997
    PORSCHE911 Convertible (993) 3.8 CarreraM 64.21S301 hp1995–1997
    PORSCHE911 Targa (993) 3.8 CarreraM 64.21S301 hp1996–1997
    PORSCHE911 (993) 3.8 Carrera 4M 64.21S300 hp1995–1997
    PORSCHE911 Convertible (993) 3.8 Carrera 4M 64.21S301 hp1995–1997
    PORSCHE911 (993) 3.8 Carrera RSM 64.20300 hp1995–1997
    PORSCHE911 (993) 3.6 Turbo 4M 64.60408 hp1995–1997
    PORSCHE911 (993) 3.6 Turbo 4M 64.60405 hp1995–1997
    PORSCHE911 (993) 3.6 Turbo GT2M 64.60R430 hp1995–1997
    PORSCHE911 (993) 3.6 Turbo GT2 4M 64.60R430 hp1995–1997
    PORSCHE911 (993) 3.6 Turbo GT2 4M 64.60RS450 hp1997