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ACL trimetal connecting rod bearings Subaru FB16 FB20 FB25

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Set of 8 trimetal connecting rod half-bearings for Subaru FB16, FB20, FB25.

  • Brand and treatment: ACL Race
  • Compatibility: Forester, Impreza, Legacy, Outback, XV
  • Engine codes: FB16, FB20, FB25
  • Available sizes: standard to +0.25 mm, increased-clearance version (HX)

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69,84 € tax incl.

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73,51 € tax incl.

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  • The Subaru FB16, FB20 and FB25 boxer engines

    The FB16, FB20 and FB25 are the 1.6, 2.0 and 2.5 litre 16-valve flat-four engines of Subaru's FB family; they power the Crosstrek, Exiga, Forester, Impreza, Legacy, Levorg, Outback and XV. ACL lists a single bearing set for these engines: same crankpin diameter, 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 8 half shells, four pairs for a four-cylinder engine.

    The original bearing relies on an aluminium alloy over a steel back, intended for low to medium loads, whereas trimetal is designed for high, sustained loads: an aluminium bi-metal takes around 8,000 psi, a performance trimetal up to 12,000 psi, 50% more. Hence better resistance and better durability on turbocharged, supercharged and high-revving engines.

    Technical specifications

    Fitment dimensions common to all references
    ACL bearings
    Crankpin Ø 47.976 / 48.000 mm
    Housing bore Ø 51.000 / 51.024 mm
    Width 13.35 mm
    ReferenceBrand and treatmentSizeWall thickness (mm)
    4B8325H-STDACL Race - UntreatedStandard1.504
    4B8325HX-STDACL Race - UntreatedStd, increased clearance (HX)1.491
    4B8325H-.025ACL Race - Untreated+0.0251.517
    4B8325H-.25ACL Race - Untreated+0.251.629

    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 reground0.051 to 0.061 mm
    Increased clearance (HX)Wider clearance: high oil flow, high rpm0.077 to 0.086 mm
    +0.025 mmPolished journal0.051 to 0.061 mm
    +0.25 mmJournal reground to 0.25 mm0.051 to 0.061 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 FB16, FB20 and FB25 boxer engines of the following Subaru models:

    BrandModel (chassis)Engine codePowerYears
    SUBARUCROSSTREK (GU_) 2.0 i AWD (GU7) / 2.0 i e-BOXER AWD (GUE) / 2.5 AWD (GU9) / 2.0 e-BOXER Hybrid AWD / 2.0 e-BOXER Hybrid AWD (GUE) / 2.0 (GUD) / 2.0 i AWD (GU) / 2.0 (GUE)FB20, FB20C, FB20D, FB20W, FB25, FB25D136–185 hp2023–
    SUBARUEXIGA (YA_) 2.5 AWD (YAM)FB25173 hp2012–
    SUBARUFORESTER (SH_) 2.0 AWD (SHJ) / 2.5 AWD (SHM)FB20, FB25150–171 hp2010–
    SUBARUFORESTER (SJ_) 2.0 i AWD (SJ5) / 2.5 AWD / 2.5 AWD (SJ9) / 2.0 BiFuel AWD (S13, SJ5)FB20, FB20A, FB20B, FB25148–173 hp2012–
    SUBARUFORESTER (SK_) 2.0 e-Boxer Hybrid AWD (SKE) / 2.5 AWD (SK9) / 2.0 AWD (SK7)FB20C, FB20D, FB20W, FB20X, FB25C, FB25D145–185 hp2018–
    SUBARUIMPREZA Hatchback (GP_) 1.6 i (GP2) / 1.6 i AWD / 2.0 (GP6) / 2.0 AWD (GP7) / 2.0 Hybrid AWD (GPE) / 1.6 i AWD (GP3)FB16, FB16A, FB16B, FB20, FB20A, FB20B114–150 hp2011–
    SUBARUIMPREZA Hatchback (GT_) 1.6 i (GT2) / 1.6 i AWD (GT3) / 2.0 i (GT6) / 2.0 i AWD (GT7) / 1.6 i (GT3) / 2.0 e-BOXER Hybrid (GTE) / 2.0 i AWD (GTE)FB16A, FB16B, FB20, FB20C, FB20W114–156 hp2016–
    SUBARUIMPREZA Hatchback (GU_) 2.0 i AWD (GU7) / 2.5 AWD (GU9) / 2.0 AWD (GU7) / 2.0 (GU6) / 2.0 e-BOXER Hybrid AWD (GUE)FB20C, FB20D, FB20W, FB25D136–185 hp2023–
    SUBARUIMPREZA Saloon (GJ_) 2.0 AWD (GJ7) / 1.6 (GJ2) / 1.6 AWD (GJ3) / 2.0 (GJ6)FB16, FB16A, FB16B, FB20A, FB20B114–150 hp2011–
    SUBARUIMPREZA Saloon (GK_) 2.0 i AWD (GK7) / 2.0 i (GK6) / 1.6 (GK2) / 1.6 AWD (GK3) / 1.6FB16A, FB20C114–156 hp2016–
    SUBARULEGACY V (BM) 2.5 AWD (BMM) / 2.5 i AWD (BMM) / 2.5 i AWDFB25, FB25A, FB25B173–177 hp2012–
    SUBARULEGACY V Estate (BR) 2.5 i AWD (BRM) / 2.0 i AWD (BRJ) / 2.5 CNG AWDFB20, FB20A, FB25, FB25B150–173 hp2012–2014
    SUBARULEGACY VI (BN) i AWD (BN9)FB25171 hp2020–
    SUBARULEGACY VII 2.5 AWDFB25D185 hp2019–
    SUBARULEVORG 1.6 AWD (VM4) / 2.0 AWDFB16, FB20A, FB20B150–170 hp2015–
    SUBARUOUTBACK (BR) 2.5 i AWD (BRM) / 2.5 CNG AWD / 2.5 BiFuel AWDFB25B173 hp2013–
    SUBARUOUTBACK (BS) 2.5 AWD / 2.5 AWD (BS9) / i AWD (BS9)FB25, FB25A, FB25B, FB25Z171–175 hp2014–
    SUBARUOUTBACK (BT) 2.5 AWD (BT9) / 2.5 AWD (BT9KL, BT9LL, BT11A, BT12A, BT13A)FB25C, FB25D169–188 hp2019–
    SUBARUXV (_GP_) 1.6 i AWD (GP3, G33GP) / 2.0 i AWD (GP7, G33GP) / 2.0 Hybrid AWD (GPE, GP7) / 2.0 Hybrid AWD (GPE) / 2.0 i AWD / 1.6 BiFuel AWD (G33GP, GP3) / 2.0 BiFuel AWD (G33GP, GP7)FB16A, FB16B, FB20, FB20-MA1, FB20A, FB20B, FB20W114–163 hp2012–2017
    SUBARUXV (GT, G24) 2.0 i AWD (GT7) / 1.6 AWD (GT3) / 2.0 AWD (GT7) / 1.6 i AWD (GT3) / 2.0 i e-BOXER AWD (GTE) / 2.5 AWD (G24)FB16A, FB20C, FB20D, FB20V, FB20W, FB20X, FB25D114–185 hp2017–