ACL Rod Bearings Honda K20 K24 – Race Series 4B1972H-STD

Description

ACL Rod Bearings Honda K20 K24 – Race Series 4B1972H-STD

Whether it’s a K20A2 from a Civic Type R EP3, a K24 bottom end for a K-swap or a turbo K20C1, the ACL Rod Bearings Honda K20 K24 set 4B1972H-STD is the Race Series big end bearing ACL specifies. The set contains 8 identical half shells, enough for all four connecting rods.

Check your engine code first. The K20A3 is the exception in the K20 family and uses a different ACL rod set (4B1906H). Contact us if you’re building one.

Race Series features

• F781 tri-metal material on a steel back, with a copper-lead-tin lining, nickel barrier and lead-tin-copper overlay.
• Hardened steel backs on all rod bearings, for lining support and retention in the big end.
• Thinner overlay on the rod shells, for better fatigue strength under high cylinder pressure.
• More crush and more eccentricity than standard shells. These help retention and oil film formation when the rod bore distorts at high rpm.
• No flash plating on the backs, which maximises heat transfer and grip in the housing.
• Tight, consistent wall tolerances for predictable clearances across all four rods.

4B1972H-STD specifications

• Size: STD (standard crank). Half type: identical halves.
• Crank pin size: 47.98–48.00mm. Rod housing size: 51.004–51.024mm.
• Max wall at crown: 1.5mm. Max overall length: 15.4mm.
• Vertical oil clearance (catalogue): 0.020–0.055mm.

ACL also lists an extra-clearance 4B1972HX-STD (+0.025mm), a dowelled 4B1972HD, and 0.025mm and 0.25mm sizes. Choose the shell after measuring the crank pins and rod bores, not just from the markings on your old bearings.

Matching K-series parts

The K20 and K24 use the ACL main bearings for the K20 and K24 (5M1959H, except the K20C1) and the ACL 1T1957 thrust washers. You can also choose all three from the ACL bearing set for the Honda K20 and K24. See more in our ACL Bearings range, or check applications in the ACL Race Series catalogue.

Engines this rod bearing set fits

• Honda K20A2 (1998cc)
• Honda K20Z1
• Honda K20C1 (1996cc turbo, Type R 2015 on)
• Honda K24A (including K24A1, K24A3, K24A4, K24A8)
• Honda K24Z1

Not for the K20A3, which uses ACL 4B1906H.

Honda models this fits

• Honda Civic [EP/EP3] (2001-2005) – Civic Type R EP3 (K20A2) – not the 1.6 EP2
• Honda Integra [DC5] (2001-2006) – Integra Type R DC5 (K20A, Japanese import)
• Honda Accord [Cl7] (2004-2008) – Accord 2.4 (K24A) – not the 2.0
• Honda Civic [FK7/FK8] (2017-2021) – Civic Type R FK8 (K20C1) – not the FK7
• Honda Civic [FL5] (2023+) – Civic Type R FL5 (K20C1)