3306 Cylinder Block – Counterbore For Liner Seat Inserts

Counterbore only the block liner seats that exhibit measurable erosion of 0.025 mm (0.001 in) or greater. Generally, liner seat erosion resulting from a head gasket failure require counterboring only one or two cylinder liner seats. Use only stainless steel inserts. The part numbers are 9L5855, 9L5856, 9L5857 and 9L5858.

Protected crankshaft journal.

When machining work is done on a cylinder block, special precautions are required to protect other engine components from contamination. Protect the crankshaft rod journals adjacent to the repair by covering with paper towels and taping. Cover the lifter bore area with paper towels or foam inserts. Tape or coat with heavy grease the oil supply dowel to prevent chip entry.

Installation of counterbore tool.

Install counterboring tool and tighten the hold down bolts to a torque of 68 N·m (50 lb ft). A counterboring tool, equipped with a dealer fabricated handle for continuous rotation of the tool, provides a smoother cut than a tool equipped with a “Tee” style handle. Continuous rotation of the tool reduces tool chatter caused by start-stop rotation. Machine a maximum of 0.10 mm (.004 in) for any one dial setting.

Depth gauge.

Use depth gauge to measure progress when nearing the depth needed to install the thinnest insert. Reduce machine depth to .025 mm (0.001 in) per cut until reaching the final depth. Measure to verify actual insert thickness and install insert so that it is flush with the top of the block within 0.013 mm (.0005 in).

NOTE: The bore in the block for the insert should be 144.051 ± 0.025 mm (5.671 ± .001 in).

Left: A good counterbore. Right: Chatter marks must be cleaned up before assembly.

Counterbore machining.

If counterboring to the depth of the thinnest insert does not clean up 100 percent of the erosion/crack damage, machine to the depth of the next insert.

NOTE: At the time of installation, the stainless steel inserts are installed dry (WITHOUT the use of sealants).

1. The design of insert (1) and the size of the counterbore give the insert a slip (loose) fit in the cylinder block. The outer diameter of the counterbore is 144.051 ± 0.025 mm (5.671 ± .001 in). If the counterbore has been cut correctly, the top of the insert will be even or within 0.0127 mm (0.0005 in) of the top surface (A) of the cylinder block to give the necessary projection for the cylinder liner. Location (B) shows the liner seat area that must clean up 100 percent before it is permissible to install an insert in the counterbore. The radius (C), 0.64 ± 0.13 mm (0.025 ± 0.005 in), is determined by the cutting tool.
2. There is a plus or minus tolerance for the thickness of the insert and for the depth of the counterbore. When inserts are installed in a cylinder block, there must be no more than 0.05 mm (0.002 in) difference in height between the inserts of any two counterbores that are next to each other. It is necessary then, to measure the depth of each counterbore and install an insert of the correct thickness to give the 0.05 mm (0.002 in) specification. The insert thickness should be measured prior to installation to determine the plus or minus tolerance.

Counterbore deburring.

When machining is complete, deburr both edges of the counterbore with emery paper or #400 wet-dry sandpaper. Use a wet-dry vacuum to remove cuttings from cylinder bores, water jacket and head bolt holes. Remove plastic bore plugs, foam inserts, paper towels, tape and all other protective covers. If necessary, run threaded tap down head bolt holes to remove burrs and thoroughly clean out head bolt holes. Wash down cylinder block with solvent or use pressure air to ensure block/crankshaft/lifter bore cleanliness. Install inserts dry (no sealant) with chamfer facing down.

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