LS-8260 / PT-8260 20/20 Oversize Caterpillar 3406 / C15 Block Deck / Upper Insert

Made In USA

The LS-8260 / PT-8260 20/20 Oversize Upper Counterbore Insert is a precision-machined repair insert designed to restore heavily damaged upper counterbores (block deck shim ledges) in Caterpillar 3406 and C15 engine blocks. This repair insert is intended for engine blocks that require +.020" oversize machining, providing a permanent repair when the standard-size insert is no longer sufficient.

The upper counterbore is one of the most critical machined surfaces in a Caterpillar engine. It supports the cylinder liner flange and establishes proper liner projection, which directly affects head gasket sealing, combustion pressure retention, and engine durability. When this surface becomes pitted, fretted, cracked, or damaged from liner movement, overheating, corrosion, or repeated overhauls, the engine block must be repaired before it can be returned to service.

The LS-8260 is manufactured with a +.020" oversize outside diameter, allowing machine shops to remove additional damaged material while restoring the upper counterbore to OEM geometry. After the damaged counterbore is machined, the insert is press-fit into the block and finish-machined to establish the proper liner seating surface.

This repair restores:

• Proper cylinder liner support
• Accurate liner projection
• Correct shim seating
• Reliable combustion sealing
• Long-term head gasket durability

Compared to replacing a cylinder block, installing an oversized repair insert provides a cost-effective solution while maintaining OEM-quality repair standards.

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Key Features & Benefits

• Precision +.020"/+.020" oversize upper counterbore repair insert
• OEM Reference: PT-8260
• Restores damaged Caterpillar block deck shim ledges
• Designed for Caterpillar 3406 and C15 engine blocks
• Allows additional machining where standard inserts cannot be used
• Restores proper cylinder liner support and alignment
• Helps maintain correct liner projection and head gasket sealing
• Precision-machined for professional engine rebuilding
• Manufactured from high-quality cast iron for long service life

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Engine Coverage

Designed for Caterpillar engines including:

• Caterpillar 3406A
• Caterpillar 3406B
• Caterpillar 3406C
• Caterpillar 3406E
• Caterpillar C15
• Additional Caterpillar 3406/C15 applications utilizing this counterbore design.

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Typical Applications

• Upper counterbore restoration
• Block deck repair
• Cylinder liner shim ledge repair
• Engine block salvage
• Complete engine overhaul
• Heavy-duty diesel machine shop rebuilding

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Why It Matters

On Caterpillar 3406 and C15 engines, liner projection is everything. Even a few thousandths of an inch outside specification can reduce cylinder head clamping force and dramatically shorten head gasket life. Caterpillar's overhaul procedures emphasize measuring liner projection after counterbore repair because improper liner height is one of the leading causes of repeat engine failures.

The LS-8260 provides the next repair step when a standard insert is no longer sufficient, allowing severely damaged blocks to be restored while maintaining the precision required for long-term engine reliability.