The LS-8320 (PT-8320) Lower Repair Ring Finished Bore Bushing is an engineered repair insert used to restore the lower repair ring bore in Caterpillar 3400-series engines (including 3406, 3408). It serves as a finished bore, precisely machined bushing that reinstates a uniform, hardened seating surface for lower repair rings when the original bore has been worn, damaged, pitted, or over-machined.
This bushing allows rebuilders to salvage engine blocks by installing a drop-in repair collar rather than replacing the entire casting or performing extensive machining. Because it restores bore concentricity and dimensional control, the insert supports accurate sealing and long life of the lower repair ring.
Key Features & Benefits
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Specifically designed for Caterpillar 3400 / 3406 / 3408 engine group
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Finished inside diameter, ready for immediate use no chamfering required
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Restores lower ring bore integrity after wear, corrosion, or rework
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Reduces need for costly re-machining of the block
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Machined to tight tolerances to maintain concentricity and sealing
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Durable repair solution that extends block life
Usage & Application Notes
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Suitable for use when the original repair ring bore is compromised by wear or damage
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Insert must be installed with appropriate press fit or heating methods per rebuild standards
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After insertion, final chamfering or honing may not be required since it is a “finished bore” design
