Usage:
D342 Engines
Description of Change: An improved cylinder block is used on all 5.75" bore, six cylinder engines. With the new design cylinder block, spacer plates are used between the cylinder block and the cylinder heads. The former cylinder block had counterbores machined in its top surface for the cylinder liners. Some times cracks were found in the counterbores under the cylinder liner flanges. In addition to the new cylinder block, new improved cylinder heads, new improved cylinder head gaskets and other parts are used. A list of the changes and improvements follows:
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- 1. The new cylinder heads have a stronger casting than the former cylinder heads. Bolts are used to hold the new cylinder heads. Formerly, studs in the cylinder block were used to hold the cylinder head. This change will make it easier to clean the top of the cylinder block during a repair. Also, additional bolts are used around the push rod compartment and all of the bolts are tightened to a higher torque than the former design.
- 2. The improved cylinder head gaskets have wire rings at the openings for the cylinders. The wire rings give a better seal. Also, the new cylinder head gaskets are one piece with additional bolt holes around the push rod compartment. The additional bolts will give more even force on the gasket to prevent oil leaks.
- 3. New seals are used for the coolant passages between the cylinder heads and the cylinder block. The new seals give a positive seal at both ends of the coolant passages. The new cylinder heads do not have counterbores in their bottom surface for the seals like the former heads.
- 4. New rear lifting eyes are used on the industrial and marine engines.
- 5. An improved cylinder head assembly is available for parts service on engines equipped with the former cylinder block. The new cylinder head assembly has a stronger casting.
- 6. An improved gasket for the push rod compartment is available for parts service on engines that have the former cylinder block. The new gasket will give a better seal against oil leaks from the push rod compartment.
- 7. Cylinder block groups for parts service on engines that have gasoline starting engines have new rods and a coupling to permit connection of the linkage for the compression release mechanism in a different location.
- 1. The new cylinder heads have a stronger casting than the former cylinder heads. Bolts are used to hold the new cylinder heads. Formerly, studs in the cylinder block were used to hold the cylinder head. This change will make it easier to clean the top of the cylinder block during a repair. Also, additional bolts are used around the push rod compartment and all of the bolts are tightened to a higher torque than the former design.
Adaptable To: The new cylinder block is adaptable to all D342 Engines. Chart 2 gives a list of the serial numbers. Extra parts are needed for engines that were equipped with the former cylinder block.
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Do not use the 7N3642 Cylinder Head Gasket on engines that had the former cylinder block. The result can be a failure of the cylinder head gasket and engine damage.
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Chart 2 shows the parts needed to install the new cylinder block in an engine that had the former cylinder block. Since the former cylinder block is canceled, the new parts will be sent if the former cylinder block is ordered. Be sure to check the engine serial number before you order the parts.
Chart 3 gives the part numbers of cylinder head assemblies for parts service on engines that have the former cylinder block. Also shown are part numbers of cylinder head assemblies for parts service on older engines that had the new style cylinder block already installed.
Procedure To Tighten Cylinder Head Bolts
The torque to tighten the cylinder head bolts on engines with the new style cylinder block is higher than for engines with the former cylinder block.
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Do not tighten the nuts for the cylinder heads on engines with the former cylinder block to the new higher torque. This can cause a failure of the threads on the studs. Tighten the nuts to the torque shown in the Service Manual.
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The procedure to tighten the bolts for the cylinder heads on engines with the new style cylinder block will be added to the Service Manual at a later date.
Use the procedure that follows to tighten the cylinder head bolts on engines with the new style cylinder block.
1. Tighten bolts 1 through 13 in number sequence to 75 lb ft (100 N·m).
2. Tighten bolts A through H in letter sequence to 210 lb ft (284 N·m).
3. Tighten bolts A through H in letter sequence to 420 lb ft (565 N·m).
4. Tighten bolts 1 through 13 in number sequence to 150 lb ft (205 N·m).
5. Use a torque wrench to tighten bolts 14 through 19 in number sequence to 75 ± 10 lb ft (100 ± 14 N·m).
6. Use a torque wrench to tighten bolts A through H in letter sequence to 420 lb ft (565 N·m).
7. Use a torque wrench to tighten bolts 1 through 13 in number sequence to 150 lb ft (205 N·m).
Schematic of cylinder head bolts.