Mitsubishi Cylinder Block for CAT 320B | S6K | OEM 34460-00052

Technical Q&A: Mitsubishi S6K Cylinder Block

Why do S6K cylinder blocks crack between the cylinders?

Thermal stress from heavy digging cycles in tropical and desert climates frequently causes metal fatigue between the cylinder bores. The Mitsubishi S6K block, heavily utilized in CAT 320B excavators, operates under extreme payload conditions. If coolant flow becomes restricted by scale buildup or inadequate maintenance, localized boiling and heat soak occur rapidly. This extreme temperature differential leads to micro-cracking in the deck surface. Our high-density cast iron replacement blocks feature reinforced cooling jackets and optimized water passages to actively prevent this thermal cracking, completely restoring engine integrity and preventing costly fleet downtime for heavy construction operations.

Is the Mitsubishi 34460-00052 block compatible with CAT 5I-7630?

Yes, the Mitsubishi 34460-00052 and the Caterpillar 5I-7630 are fully interchangeable. Because Mitsubishi manufactured the S6K engine specifically for Caterpillar’s E200B and 320B excavator lines, the core cylinder block castings share identical dimensions, bore spacing, and bell housing bolt patterns. This exact OEM-spec block ensures plug-and-play fitment for engine rebuilders, eliminating the need for any custom machining during your rebuild.

Does the bare block assembly include the main bearing caps?

Yes, our bare cylinder block assembly comes complete with the original factory-matched main bearing caps. It is critical to understand that main bearing caps are line-bored perfectly to the specific engine block at the factory. You cannot swap main caps from an old engine onto a new block without causing severe crankshaft misalignment. All our S6K blocks are pre-aligned and ready for immediate crankshaft installation.

How do I prevent cylinder liner wear in the new S6K block?

Cylinder bore wear in the S6K engine is typically accelerated by abrasive dust ingestion in heavy mining or construction environments, combined with localized overheating. For the S6K block, which utilizes dry cylinder liners, maintaining perfect block-to-liner contact is essential for heat transfer. If the block is warped, the liners will suffer from cavitation and rapid wear. Our 34460-00052 cylinder blocks are CNC-machined to exact factory tolerances, ensuring your replacement dry sleeves seat perfectly. Always flush the cooling system and use high-quality coolant to prevent cavitation and maximize the lifespan of your heavy-duty rebuild.