2000/01/01 Caterpillar

New Basic Cylinder Head Groups Include Premachined Valve Seat Inserts For Improved Reliability {1100}

Usage:

Engines: G3606 (S/N: 3XF1-UP) G3608 (S/N: 4WF1-UP) G3612 (S/N: 1YG1-UP) G3616 (S/N: 4CG1-UP)

Description of Change: New basic cylinder head groups are used on these engines. The new cylinder heads include new premachined valve seat inserts and precision valve guides. The premachined inserts provide the following advantages:

improved reliability
simplified field service

The new premachined seat inserts provide improved concentricity of the seating surface. The manufacturing process has been improved so that no machining of the valve seats is necessary after installation.

Adaptable To: The new cylinder heads are effective with the following engines: G3606 (3XF214-UP), G3608 (4WF141-UP), G3612 (1YG179-UP) and G3616 (4CG152, 153, 155-UP). The new cylinder heads are adaptable to earlier engines that have the listed serial number prefixes.

The part numbers for the new basic cylinder head groups and the former basic cylinder head groups are listed in Table 1. The basic cylinder head groups are components of the respective cylinder head groups that are listed in Table 1.

Note: The cylinder head groups are not available for parts service. The cylinder heads are serviced at the "basic cylinder head group" level.

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Table 1
Components of the Cylinder Head Groups
Application	Cylinder Head Group Part Number ⁽¹⁾	New Basic Cylinder Head Group Part Number	Reman Pt. No. for New Basic Cylinder Head Group	Former Basic Cylinder Head Group Pt. No.
Natural Gas (Low Compression)	7C-0400	171-3994	0R-9794	155-4093
Natural Gas (High Compression)	N/A	171-3995	0R-9752	161-1205
Landfill Gas	172-2227	171-3996	0R-9753	148-3056

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These part numbers are not serviced. The cylinder heads are serviced at the "basic cylinder head group" level.

The components that are listed in Table 2 can be used to rebuild the new cylinder heads. The premachined valve seat inserts MUST be used with the precision valve guides. The part numbers for the valves have not changed from the former cylinder heads.

Note: The new cylinder head components are not adaptable to the former cylinder heads.

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Table 2
Major Components of the New Basic Cylinder Head Groups
Basic Cylinder Head Group	Inlet Valves	Exhaust Valves	Valve Guides	Cylinder Head Assembly ⁽¹⁾	Inlet Valve Seat Inserts ⁽¹⁾	Exhaust Valve Seat Inserts ⁽¹⁾
171-3994	4P-2854	154-2417	175-6344	170-7740	171-3992	171-3993
171-3995	4P-2854	149-0588	175-6344	170-7740	171-3992	171-3993
171-3996	4P-2854	9Y-6232	175-6344	170-7741	171-3992	160-5770

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The valve seat inserts are components of the cylinder head assemblies. The inserts are available individually for parts service. The cylinder head assemblies are not available for parts service.

Note: Do not perform any machining or any lapping on the valves or seat inserts after installation. Proper seating is established very early in the break-in period.

Note: It is VERY IMPORTANT to perform bridge adjustment and valve lash adjustment at the proper interval. The recommended interval for each specific application can be found in the Operation and Maintenance Manual for the engine.