VALVE GP-IMPL 5203397 - Caterpillar

3400 Series EnginesThe recommendation has changed for the position of the oil hole during installation of the camshaft bearings.
The correct position for the oil hole in the camshaft bearing is on the horizontal centerline of the bearing bore. This position is 90 15° away from the oil hole in the block and will ensure that the oil hole is not located in a highly loaded area.
The outside of the camshaft bearing has a groove running around its circumference. This allows the oil to flow from the cylinder block, around the camshaft bearing and out the hole in the bearing to lubricate the camshaft.
Formerly the oil holes in the bearings were aligned with the oil holes in the block bore. This is the procedure shown in the Service Manual for these engines. This procedure put the bearing oil hole in a highly loaded area. The result was less bearing surface in the area that carries the load.
The interruption of the smooth surface due to the oil hole can also result in a loss of oil film in the event of minimum lubrication.
Make a note in your Service Manual of this change.