1981/10/21 Caterpillar

3406, 3408, 3412 Industrial And Marine Engines

Some of the Service Manual information about inside diameters of valve guides for the above engines is not complete, or is not the same in the "Disassembly and Assembly" section as in the "Specifications" section. The correct dimensions are:

... Valve guide inside diameter (installed, new) -.3735 ± .0010 in. (9.487 ± 0.025 mm).

... Maximum diameter for a used valve guide (wear limit) - .3758 in. (9.545 mm).

In the Service Manuals, the inside diameter for new valve guides is shown in the "Specifications" section and in the "Disassembly and Assembly" section. This dimension is shown correctly in the "Specifications" section of all the Service Manuals, but a wrong dimension is shown in the "Disassembly and Assembly" section of two Service Manuals. In the "Disassembly and Assembly" section of the Service Manual for 3408 Industrial and Marine Engines, Form SEBR0502, and for 3412 Industrial and Marine Engines, Form SEBR0503, change ".3732 ± .0008 in. (9.479 ± 0.020 mm)" to read ".3735 ± .0010 in. (9.487 ± 0.025 mm)".

The maximum diameter for a used valve guide (wear limit) is normally shown in the "Disassembly and Assembly" section, but is not shown in one Service Manual. Add the wear limit dimension of .3758 in. (9.545 mm) to the Service Manual for 3406 Industrial and Marine Engines, Form SEBR0510.