2003/06/01 Caterpillar

Engine:

G3600

The prechamber assembly on G3600 engines was originally designed with 3/8 inch hold-down bolts. These bolts are located on the top face of the cylinder head. Recent changes to the design of the prechamber assembly have resulted in the use of 1/2 inch hold-down bolts.

Some existing cylinder heads can be converted from 3/8 inch hold-down bolts to 1/2 inch hold-down bolts. This article provides the following information:

• Part numbers of the cylinder heads that can be modified

• Modifications to the cylinder head and to the prechamber assembly

• Guidelines for cleaning the gasket surfaces

• New hardware requirements

• Torque procedure for the new 1/2 inch bolts

Cylinder Heads That Can Be Modified

Table 1 lists the part numbers for the cylinder head groups that can be modified. These groups contain a 170-5077 Cylinder Head. The part number for the head is cast into the passage for the intake air.

Note: Modifying these cylinder heads does not change the core credit status of the cylinder heads. However, core credit for the cylinder head may be denied if the cylinder head is improperly modified or if the cylinder head is damaged during the modification.

Modify the Cylinder Head and the Prechamber Assembly

Note: Modifications to a cylinder head must be performed by a qualified Caterpillar dealer technician.

Note: The cylinder head must be removed from the engine before the cylinder head is modified. If the cylinder head remains on the engine during the modification, metal chips may contaminate the cylinder head or other engine components. Severe engine damage may result.

1. Remove the cylinder head from the engine.

2. Remove the prechamber assembly from the cylinder head.

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Illustration 1	g01001377
Specifications for modifying the cylinder head

3. Modify the cylinder head according to the specifications in Illustration 1. Proper alignment of the drill bits and the tap drill is required in order to obtain the correct dimensions. A magnetic drill fixture or a drill press must be used in order to properly machine the cylinder head to the new dimensions.

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Illustration 2	g01001384
Top view of the flange on the prechamber assembly

4. After you secure the prechamber assembly in an appropriate fixture, modify the prechamber assembly according to the specifications in Illustration 2.

Clean the Gasket Surfaces

Note: Failure to provide gasket surfaces that are clean and free of defects may result in coolant leaks into the combustion chamber.

Always inspect all of the gasket surfaces on the cylinder head and on the prechamber assembly prior to reassembly of the components. Ensure that the surfaces are free of debris and of defects.

Clean the gasket surfaces on the prechamber assembly by using one of these tool groups:

• 9U-5156 Cleaning Tool Gp

• 187-6273 Machining Tool Gp

Note: The 187-6273 Machining Tool Gp may require modifications to the cutting head prior to use. Contact your local Caterpillar dealer for additional information.

After the gasket surfaces have been cleaned, perform a final cleaning. Use a towel that has been soaked with a component cleaner that does not leave any residue. The 138-8440 Component Cleaner is acceptable for such use.

New Hardware Requirements

Table 2 lists the new hardware that is required for each cylinder that has been modified.

Note: Always use a new gasket assembly for the prechamber assembly after performing any service that requires removal of the prechamber assembly from the engine.

Torque Procedure for the New 1/2 Inch Bolts

Perform the following procedure in order to properly torque the new 1/2 inch bolts:

1. Seat the prechamber assembly into the bore of the cylinder head by alternate tightening of the bolts.

   Torque ... 30 N·m (22 lb ft)

2. Loosen the bolts.

3. Alternate the tightening of the bolts.

   Torque ... 30 ± 5 N·m (22 ± 4 lb ft)

4. Place an index mark on each bolt. Tighten the bolts for 30 degrees.

5. Tighten the bolts for an additional 30 degrees.

6. Tighten the bolts for an additional 60 degrees.

   Note: The total degrees of rotation for each bolt from the initial torque is 120 degrees ± 5 degrees. Overtightening the bolts may shorten the life of the bolt. Inadequate tightening can lead to an inadequate load on the gasket. This may result in coolant leaks into the combustion chamber.