3406, 3408 Truck Engines
Some dealers have desired information about a change which was made to pistons for the 3400 Series Engines. The piston design was changed to use a total of four oil drain holes in the bottom ring groove, in comparison with the fourteen holes formerly used. The four holes are drilled only at the sides of the piston body, two holes on each side. This change in the number of drain holes has no effect on engine oil consumption.