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King Engine Bearings MB5278XP0.25 XP-Series Tri-Metal Main Bearing Set Ford 140ci 2.3L L4

(1991-1993 Ford Mustang; 1989-2001 Ford Ranger; 1996-2000 Ford F-100 Ranger; 1998-2001 Mazda B2500; 1985-1989 Merkur XR4Ti)

Manufacturer

Picture for manufacturer King Engine Bearings

Part Number

MB5278XP0.25
12 reviews
Sale Price

$184.24

Estimated ship date Saturday, December 05

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Product Details

The King Engine Bearings MB5278XP0.25 is a complete XP-Series crankshaft main bearing set engineered for the Ford 140ci (2.3-liter) inline four-cylinder engine. Sized at 0.25mm undersize, this set is designed for high-performance and racing applications demanding sustained reliability under extreme load.

King's XP-Series bearings are built around the proprietary pMaxBlack tri-metal construction — an advanced copper/lead intermediate layer with a nickel barrier and lead/tin/copper Babbitt overlay, all bonded to a high-strength steel backing via King's SecureBond adhesion process. This layered structure delivers 15–30% greater load capacity than traditional bearings and a performance overlay that is 24% harder than conventional tri-metal race bearings.

Key Features:

  • Tri-Metal pMaxBlack Construction: Copper/lead intermediate layer, nickel barrier, and hardened Babbitt overlay over steel backing for superior fatigue resistance and load capacity
  • SecureBond Adhesion Process: Provides exceptional stability and durability between bearing layers
  • Bull's Eye Tolerance: Wall thickness tolerance of ±0.0001" — the tightest in the industry — ensures consistent fit and minimal adjustment during assembly
  • Enlarged, Chamfered Oil Holes: Promotes improved oil flow and lubrication to critical surfaces
  • Narrowed Design: Accommodates large-radius crankshafts common in performance builds
  • Medium Eccentricity: Optimizes load distribution and enhances oiling characteristics
  • 0.25mm Undersize: Engineered for reground crankshafts turned to 0.25mm undersize
  • High-Load, Long-Duration Rating: Ideal for circle track, off-road, offshore racing, and other sustained high-performance applications using forged steel crankshafts

King Engine Bearings has specialized exclusively in engine bearings since 1960, and the XP-Series represents their top-tier race bearing line. The MB5278XP0.25 is a direct-fit replacement main bearing set providing a measurable performance and durability upgrade over OEM-spec bearings for the Ford 2.3L L4 engine.

Products specifications

Fits

1991-1993 Ford Mustang; 1989-2001 Ford Ranger; 1996-2000 Ford F-100 Ranger; 1998-2001 Mazda B2500; 1985-1989 Merkur XR4Ti

Flange Oversize

FL STD

Material

pMax Black (racing line)

Undersize

0.25

STD Max Thickness

2.423

Shaft UnderSize

0.25mm

Housing Diameter

60.91 / 60.89 mm || 2.398 / 2.397 inch

STD Shaft Diameter

56.03 / 56.01 mm || 2.206 / 2.205 inch

Thanks fast ordering

lowest prices

Quick search and your site came up with exact part needed. Checkout was super simple!

So far so good

GOOD

Search to ID the right part looks good so I bought. Sure hope it fits!

nice

It was good.

Website is precise, loads quickly. easy shopping

The prices are great. Shipping is so so, but that's normal for Alaska

so far so good

so far so good.

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