Usage:
3406 Family Of Truck Engines
Description of Change: A new cylinder head gasket is used on the 3406B Family of Truck Engines. The new gasket is coated with a single layer of silicone material on the cylinder head side and a single layer of black Teflon® material (PTFE) on the spacer plate side of the gasket. The silicone material limits adhesion to the cylinder head. The PTFE material prevents adhesion to the aluminum spacer plate.
Adaptable To: The new 9Y7786 Cylinder Head Gasket replaces the former 2W7983 Cylinder Head Gasket, which was coated with a double layer of orange Teflon® material (PTFE) on both sides. The 9Y7786 Gasket is in effect on 3406B Truck Engines 4MG32240-Up, 8TC5331-Up.
The former 2W7983 Gasket (orange colored) can be adapted to simulate the 9Y7786 Gasket by removing the double layer of PTFE material from the cylinder head mounting surface of the gasket. This can be accomplished with a clean Scotch Brite®cleaning pad and/or xylene solvent.
Cleaning Procedures
Thoroughly remove the PTFE material residue from the cylinder head bottom deck and the spacer plate during rebuild by using either method listed in the previous paragraph. This material has a tendency to stick to the head gasket mating surfaces during operation and should be removed to help eliminate future parts slippage.
Surface Inspection
Inspect the bottom deck of the cylinder head for flatness according to the Service Manual and repair if necessary.
Check the top deck of the cylinder block for flatness. Inspect for liner beat-in or erosion under the liner flange and repair with an insert. The block deck may require machining if the engine was operated extensively after a head gasket failure.
Liner Projection
Make sure liner projection is within specification during rebuild before installing new 9Y7786 Gaskets or reworked 2W7983 Gaskets. DO NOT USE 2W7983 Gaskets in repairs unless they are reworked.
On engines with aluminum spacer plates, use care in obtaining liner projection measurements to prevent marring the surface. To prevent damage to the spacer plate, use copper washers instead of hardened steel washers with the spacer plate bolts. Do not excessively tighten the spacer plate bolts.
In addition, to increase the accuracy of liner projection measurements and also prevent damage, cut "figure 8" sections from an old spacer plate and install them under the spacer plate bolts. These are the center ribs between the cylinder holes from a scrapped 2W8601 Spacer Plate as shown in the illustration. The top and bottom radii of the "figure 8" section should coincide with the radii of the washers. Refer to the Service Manual procedure in conjunction with use of the "figure 8" sections.
Rework old spacer plate to fabricate "figure 8" sections.
Aluminum Spacer Plate Reusability
The 3400 Engine uses a die cast aluminum spacer plate which weighs and costs less than the steel spacer plate which is no longer available. The aluminum spacer plate requires more care in handling and cleaning to prevent damage and retain reusability than the former steel spacer plate. Do not use a paint scraper, sander or wire brush to clean the spacer plate. Recommended cleaning materials are xylene solvent and/or Scotch Brite®cleaning pads.
To minimize external oil leakage, no cracks or connecting surface depressions are permitted in a 6 mm (.2 ") zone around the outer perimeter of both sides of the plate or around the oil drain holes. The plate surface beyond these areas may have surface depressions up to 1 mm (.04 ") deep and 5 mm (.2") diameter on either side of the plate.
Hairline (without measurable width) cracks are permitted between the large head bolt holes and the large cylinder liner clearance holes or valve pockets. Hairline cracks are also permitted between adjacent large cylinder liner clearance holes. Hairline cracks in these areas will not affect the function of the spacer plate. Do not reuse plates that show cracks with measurable width and depth which have resulted from spalling of material or scorch paths from exhaust gas leakage.
Additional Repair Considerations
While completing the engine repair, carefully evaluate the following factors that may contribute to the incorrect head gasket loading.
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- ... Verify the proper depth and cleanliness and integrity of the cylinder head bolt holes. If needed, use a tap to remove any burrs that may be present. Also, lubricate the bolt threads with clean engine oil (or 5P3931 Anti-seize Compound) prior to assembly.
- ... Verify the fuel injection system settings by checking to make sure the factory seals are in place.
- ... Make sure the cooling system is in good operating condition with winter radiator covers on truck engines used correctly.
- ... Make sure the Jacobs® Engine Brake has been installed correctly if the truck engine is so equipped.
- ... Make sure that any ether starting aids are being used correctly.
- ... Verify timing advance integrity and turbo boost levels.
- ... Check for high inlet air or exhaust temperatures caused by excessive intake or exhaust restrictions.
- ... Verify the proper depth and cleanliness and integrity of the cylinder head bolt holes. If needed, use a tap to remove any burrs that may be present. Also, lubricate the bolt threads with clean engine oil (or 5P3931 Anti-seize Compound) prior to assembly.