Engine Crankshaft Main Bearing Set

What Are Engine Crankshaft Main Bearings?

Crankshaft bearings, also called main bearings, support the crankshaft in the crankcase. As the crankshaft rotates and translates the up-and-down motion of the piston and connecting rod into circular motion, it is held in the engine block by the main bearings. They consist of two semi-circular elements, each containing a bearing shell. A main bearing set includes all of the upper and lower bearing shells needed to fully support the crankshaft journals across the entire engine block — everything required for a complete bottom-end rebuild in a single package.

Why Main Bearings Matter

Crankshaft bearings may be small and inconspicuous, but they are very important for the stability of the crankshaft and therefore an important element of performance enhancement. Very heavy loads are applied to the bearing surface through the oil film — including the firing load applied through the piston and connecting rod as each cylinder fires, and the inertia load resulting from rotation. It is the prime requirement of the bearing that it should be able to carry these loads without suffering damage.

The common crankshaft bearing has a steel backing with a thin lining of bearing alloy, and it is this construction that provides its load-carrying capability. Corrosion resistance and cavitation erosion resistance are also important properties, because the trend toward higher engine temperatures and longer oil-change intervals results in eventual degradation of engine oil, which can attack the crankshaft bearing. Selecting the correct bearing material and wall thickness for your specific application — whether a stock daily driver or a high-output performance build — is critical to long engine life.

What to Consider When Shopping Main Bearing Sets

• Material construction: Tri-metal bearings (steel backing, copper-lead middle layer, and soft overlay) offer excellent load capacity and conformability. Bi-metal aluminum-silicon designs are increasingly common in modern OEM and replacement applications.
• Sizing and clearance: Main bearing sets are offered in standard and various undersizes to accommodate reground crankshafts. Always measure your crank journals before ordering.
• Application type: Street/stock rebuilds, high-performance builds, and full racing applications each have different bearing requirements — match the bearing to the intended use.
• Quality control: Tight wall-thickness tolerances are essential. Even small deviations affect oil clearance and can lead to accelerated wear or bearing failure.

Top Brands in Engine Crankshaft Main Bearing Sets

King Engine Bearings is one of the most trusted names in the segment. Founded in 1960, King Engine Bearings is a world-class developer and manufacturer of engine bearings, and because engine bearings are King's only product, the company is recognized for producing the highest quality engine bearings available in the market today. King has developed unique features including pMaxBlack™, U-Groove™, ExcentriX™, ElliptiX™, and RadiaLock™ for demanding race and performance applications.

Clevite is another cornerstone brand for engine builders worldwide. Since the development of the first precision insert-type bearing in 1929, Clevite bearings have set the pace for engineering quality and today exceed industry standards for strength and durability. Clevite® tri-metal engine bearings have been the industry standard since the first patent on the cast, copper, lead composition decades ago.

HAZET is a renowned German precision tool manufacturer whose specialty installation tools for crankshaft main bearings ensure proper fitment during engine assembly — an essential companion for any serious engine rebuilder working to factory tolerances.

Sealed Power has long been a go-to source for engine rebuild components. Part of the Tenneco family of brands, Sealed Power offers a broad range of main bearing sets engineered to OEM specifications, making them a solid choice for restoring everyday vehicles to factory performance.