What does the '+1.0mm' sizing mean for these main bearings?

The '+1.0mm' designation indicates that these bearings are oversized by 1.0 millimeter. This sizing is used when the crankshaft journals have been machined down by 1.0mm during an engine rebuild to remove wear or damage. Using the correct oversized bearing ensures proper oil clearance and support for the crankshaft.

What is the construction of these King Engine Bearings?

These main bearings feature a bimetal construction with an aluminum base. This type of design is chosen for its ability to handle engine loads and manage heat effectively, contributing to reliable engine operation.

Are these bearings a direct replacement for all 2.3L Ford engines?

This specific main bearing set, part number MB5278AM1.0, is designed for Ford 140ci / 2.3L L4 engines and is sized +1.0mm. Always verify your engine's specific requirements and the condition of your crankshaft journals before ordering oversized bearings.

Specifications

Brand: King Engine Bearings
Part #: MB5278AM1.0
UPC: 611500401596

King Engine Bearings Ford 140Ci /2.3Liter/L4 (Size +1.0mm) Main Bearing Set

Name: King Engine Bearings Ford 140Ci /2.3Liter/L4 (Size +1.0mm) Main Bearing Set
Brand: King Engine Bearings
SKU: king-engine-bearings-king-engine-bearings-ford-140ci-2-3liter-l4-size-1-0mm-main-t14-770617
Price: 53.85 USD
Availability: BackOrder

$53.85

On Backorder — Expected to ship by Oct 31, 2026

Order now to reserve yours — we'll ship as soon as stock arrives. Full refund if we're unable to fulfill.

Fits 1989-2001 Ford Ranger. King Engine Bearings Main Bearing Set, sized +1.0mm, uses an aluminum base for reliable engine performance.

Key Features

Fits 1989-2001 Ford Ranger, 1991-1993 Ford Mustang, 1998-2001 Mazda B2500, and 1985-1989 Merkur XR4Ti.
Main bearing set for Ford 140ci / 2.3L L4 engines.
Bimetal construction with an aluminum base for durability.
Sized +1.0mm for use with machined crankshaft journals.

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About this part

Product Details

Built with an aluminum base, this main bearing set from King Engine Bearings is designed for Ford 140ci/2.3L L4 engines. These bearings are crucial for supporting the crankshaft within the engine block, ensuring it spins smoothly and with minimal friction. This particular set is sized +1.0mm, meaning it's intended for use when the crankshaft journals have been machined to a larger diameter during an engine rebuild.

King Engine Bearings uses a bimetal construction, which combines the strength of aluminum with other materials to create a well-built bearing surface. This design helps manage heat and wear, which is important for the longevity of your engine. When you're rebuilding the bottom end of your Ford Ranger, Mazda B2500, or Merkur XR4Ti, using the correct size bearings like these +1.0mm mains is essential for proper oil clearance and crankshaft support.