King Engine Bearings MB556HPSTDX Engine Crankshaft Main Bearing

King offers 3 levels of main bearings for use in OE Stock, High Performance, and Extreme Performance applications. King main bearings are sold in engine sets.



AM-Series & SI-Series Bearings:
King AM-Series & SI-Series bearings are recommended for OE applications. AM-Series bearings are aluminum-copper-tin plus Alloy on high-strength steel (Bi-Metal). SI-Series bearings are Silicon-Aluminum bearings (Bi-Metal) are designed for Aftermarket Gasoline or Diesel Engine Rebuilding & Performance Engines with OE Crankshafts.

HP-Series Bearings:
King HP-Series bearings are recommended for street and strip high performance applications. These Bi-Metal Silicon Aluminum bearings are designed for blown, turbocharged, NOS, and alcohol-fueled engines using aftermarket crankshafts. These bearings have chamfered oil holes are fit aftermarket cranks machined with a large radii at the edge of the journals. Most main bearings in the HP-Series are 3/4 grooved for improved oiling to the rod journals. Ideal for use in High Load, Short Duration Applications like Drag Racing, Tractor Pulling, Monster Trucks, etc.

XP-Series Bearings:
King XP-Series bearings are for extreme performance in high-load capacity applications. These Tri-Metal copper lead bearings are designed use on cranks with large radii (narrow rod bearings) and feature enlarged, chamfered oil holes with 1/2 grooving (on most main bearings) for uncompromised lower bearing load capacity. Ideal for use in High Load Circle Track & Endurance Applications.

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What does the King part number Prefix/Suffix mean

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NOTE: The term "Undersize" refers to a thicker bearing which is used when the Crankshaft has been turned down and is now undersized, not the bearing itself. The term "Oversize" is typically a thinner bearing than stock to allow for increased clearance.

Select your application below.

Chevy: Small Block,LS,400ci,Big Block

Chrysler: 318/340ci,426 Hemi/440ci

Ford: 289/302ci , 351C , 351W , 4.6L SOHC (Cast Iron Block) , 4.6L SOHC/DOHC (Aluminum Block) , 4.6L/5.4L SOHC Windsor ,
429/460 Big Block
Main Bearing Set

• Big Block Chevy
• HP-Series
• .001" Oversize