ACL 5M1985HX-STD Race Main Bearings +.001 Oil Clearance Honda Civic Type R K20C1

Vehicle Fitment

• 2015-2017 Honda Civic Type R (FK2, 2.0L I4 DOHC VTEC Turbo - K20C1, FWD)
• 2017-2021 Honda Civic Type R (FK8, 2.0L I4 DOHC VTEC Turbo - K20C1, FWD)
• 2023-2025 Honda Civic Type R (FL5, 2.0L I4 DOHC VTEC Turbo - K20C1, FWD)

Fitment Notes

• Designed exclusively for the Honda K20C1 turbocharged engine (1998cc Turbo Inline 4) used across all three Civic Type R generations: FK2, FK8, and FL5. Do not use on naturally aspirated K-series engines (K20A, K20A2, K20Z1, K24A, K24Z1) - those applications require ACL part numbers 5M1959H-STD or 5M1959HX-STD.
• The "HX" designation indicates this set provides +0.001" (0.025mm) extra oil clearance compared to the standard 5M1985H-STD set. The bearing wall at crown is 0.0005" (0.013mm) thinner than the H-STD. In all other respects - material, construction, crush, and eccentricity - the HX set is identical to the H-STD.
• This is a standard journal diameter set. For use only with unmachined, standard-size crankshafts. Reground crankshafts require an oversized variant; the HX designation is only available in STD journal size per the ACL application guide.
• Bearing half type is upper and lower (non-identical halves) - install per position as specified during assembly.
• Recommended for high-RPM, high-output, or forced-induction builds where additional oil film thickness is desired. Builders targeting tighter H-STD clearances for street use should consider 5M1985H-STD instead.
• Drivetrain: FWD for all listed vehicles. Manual transmission only across all Civic Type R generations.
• FK2 production was Europe and Japan only; the FK8 was the first Civic Type R officially sold in North America.

Features

• HX extra-clearance design provides +0.001" (0.025mm) additional oil clearance versus the H-STD set by using bearing shells that are 0.0005" (0.013mm) thinner at the crown - engineered specifically for high-RPM and high-output K20C1 engine builds requiring a wider oil film.
• Tri-metal F780 construction combining a high-strength steel backing, copper-lead intermediate layer, and a performance-grade overlay - delivering superior load capacity and seizure resistance under sustained turbo boost and high cylinder pressure.
• High-strength overlay plate with reduced thickness for improved fatigue resistance, allowing the bearing surface to endure extended high-RPM operation without delamination or fatigue failure.
• Hardened steel backing on all bearing shells provides stronger support for the bearing lining and improves shell retention within the housing bore under elevated combustion and inertia loads.
• Increased bearing crush for improved retention - enhanced radial contact pressure locks each shell firmly in its bore, preventing micro-movement and fretting corrosion during aggressive driving or sustained track use.
• No flash plating on bearing backs - maximizes direct contact between the shell and housing bore for superior heat transfer and grip, a critical advantage in turbocharged applications with elevated operating temperatures.
• Increased eccentricity design compensates for main bore distortion at high RPM, improving hydrodynamic oil film formation and maintaining stable crankshaft lubrication across the full journal surface throughout the power band.
• Enlarged inner diameter chamfers on bearing edges accommodate crankshafts with larger fillet radii, a common feature in performance-ground or aftermarket K20C1 crankshaft applications.
• Manufactured to micron-level tolerances using precision measurement systems, ensuring consistent wall thickness and crush across all five main journal positions for a reliable, repeatable build every time.

Specifications

• Part Number: 5M1985HX-STD
• Designation: HX - Standard journal size with +0.001" (0.025mm) extra oil clearance vs. H-STD
• Wall Thickness Difference vs. H-STD: 0.0005" (0.013mm) thinner at crown
• Bearing Material: F780 Tri-Metal
• Bearing Half Type: Upper and lower (non-identical halves)
• Position: Main crankshaft (all 5 positions)
• Min. Shaft Size: 54.980mm / 2.1646 in
• Max. Shaft Size: 55.000mm / 2.1654 in
• Min. Tunnel Size: 59.000mm / 2.3228 in
• Max. Tunnel Size: 59.020mm / 2.3236 in
• Max. Wall at Crown: 1.989mm / 0.0783 in
• Max. Overall Length: 20.00mm / 0.7874 in
• Min. Vertical Oil Clearance: 0.038mm / 0.0015 in
• Max. Vertical Oil Clearance: 0.098mm / 0.0039 in
• Quantity: Set of 5 pairs (upper and lower shells)

Included Components

• 5x Upper Main Bearing Shells (STD, HX Extra Clearance)
• 5x Lower Main Bearing Shells (STD, HX Extra Clearance)

Product Description

The ACL Race Series 5M1985HX-STD is the extra-clearance variant of ACL's purpose-built K20C1 main bearing set, designed for the Honda Civic Type R across all three generations: the FK2 (2015-2017), FK8 (2017-2021), and FL5 (2023-2025). The "HX" designation, as defined in ACL's official Race Series application guide, signifies that these shells are 0.0005" (0.013mm) thinner at the crown than the standard H-STD set - producing +0.001" (0.025mm) of additional assembled oil clearance on a standard-diameter crankshaft journal. In all other respects - tri-metal F780 material, bearing crush, eccentricity, chamfer geometry, and surface treatment - the HX set is identical to the 5M1985H-STD.

This additional oil clearance is specifically sought after by engine builders constructing high-output K20C1 builds - including time attack, drag, and endurance racing applications - where a thicker, more robust oil film is needed to protect the crankshaft under sustained high RPM, elevated oil temperatures, or increased cylinder pressures from aggressive boost targets. The wider clearance improves oil flow volume through the main journal, reducing bearing temperature and providing an added margin of safety in demanding conditions. Like all ACL Race Series bearings, the 5M1985HX-STD features a hardened steel backing, no flash plating on the bearing backs, and increased bearing crush to lock the shells positively into the housing and resist micro-movement even at the highest output levels the K20C1 is capable of producing.

Builders should note that the HX designation is only available in the standard (STD) journal diameter - there is no HX oversize variant for reground crankshafts per the ACL application guide. For standard journal builds prioritizing tighter clearances closer to OEM spec, the 5M1985H-STD is the appropriate choice. For reground crankshaft applications, refer to the 5M1985H-.25 oversized set. The 5M1985HX-STD is the preferred specification for experienced engine builders dialing in a performance K20C1 bottom end where oil clearance is measured and confirmed with precision tooling prior to final assembly.