Engines and Components› Engine Bearings

ACL

Main Bearing Set

$76.58

SKU: 5M1957H-4B1956H

Special Order
Special Order
Ships in 4–6 weeks
Free Shipping over $200
$100 Minimum Order
30 Days Return
INSTALL DIFFICULTY
DIY PRO SHOP

Moderate — 2–4 hours

Overview

The ACL 4B1956H is a set of high-performance engine bearings designed for demanding applications. The bearings utilize identical halves for consistent installation.
Show original supplier description
The ACL Race Series engine crankshaft main bearing set (part number 5M1957H-4B1956H) offers superior performance and durability for racing engines. These bearings are constructed with a high-strength overlay plate and reduced thickness for improved fatigue resistance, a critical factor in high-RPM environments. Engineered with a unique combination of design, metallurgy, and engineering, the RACE Series bearings are built to endure where others might fail. They feature hardened steel backs for better support and retention, increased crush for improved grip, and elimination of flash plating on the back to enhance heat transfer. The design also includes increased eccentricity to compensate for bore distortion and assist in forming hydrodynamic oil films, alongside 3/4 grooved main bearings for optimized load carrying and oil flow. These bearings boast tight, consistent wall tolerances for precise clearances and incorporate enlarged ID chamfers to accommodate performance crankshaft fillet radii. They are available in STD, .025, and .25 sizes, with specifications including identical halves, F781 material, and dimensions such as a maximum wall at crown of 1.499 mm and a maximum overall length of 18.5 mm.

Product descriptions are provided by our supplier partners and may not always be perfectly accurate. Not sure this fits? or call (760) 282-4645 and we’ll verify before you order.

Fitment

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Specifications

BrandACL
Part Number5M1957H-4B1956H
CategoryEngines and Components
5,000+ Trusted brands
1M+ Enthusiasts
5M+ Parts sold
(760) 282-4645 hello@motormia.co

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Returns & Fitment

Built for enthusiasts. Every order is backed by our 30 day return window on eligible items. Unused and uninstalled products may be returned with approved RMA and no restocking fees when received in new condition. Orders placed through the MOTORMIA app with a complete build qualify for our Fitment Guarantee — free return shipping if the part doesn’t fit your exact setup. The guarantee covers fit only; installation must follow manufacturer instructions, and we recommend a qualified shop for parts marked Difficulty 4–5.

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Shipping

Orders are processed in 1–3 business days. In stock parts ship promptly from our partner network. Special-order items either aren’t currently stocked or are built to your spec — expect 4–6 weeks. If a part goes on backorder while your order is in the queue, we’ll reach out and work through discounted alternatives together.

Free shipping over $200 in the continental US. Alaska, Hawaii, U.S. territories (Puerto Rico, U.S. Virgin Islands, Guam, American Samoa, and the Northern Mariana Islands), and international orders carry surcharges — most appear at checkout. Some exceptions (LTL freight, or suppliers who quote freight only after we place the order) won’t. In those cases we’ll reach out with the exact charge before your order moves forward.

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