Crankshaft Main Bearing: Description and Operation

DESCRIPTION





The bottom of the cylinder block has provisions for mounting the main bearing caps and the oil jets. Four main bearing caps (1) made of gray cast iron are bolted to the cylinder block. Each main bearing cap has six mounting bolts, four vertical and two horizontal. The horizontal (cross) bolts add increased rigidity to the cylinder block.

The number three main bearing cap serves as the thrust washer (5) location.

The upper main bearings have a bi-metal construction and feature oil supply holes and center grooves for lubrication of the main journals. The lower main bearings have tri-metal construction to provide strength where it is needed.





The upper main bearings are available in three different thicknesses and the lower bearings in five. A color coded mark on the side of the bearing is used to identify it's thickness. Each color coded bearing is matched to it's respective journal. The select fit is obtained by matching the color coded bearings to grade identification marks on the cylinder block and crankshaft. Letters marked on the cylinder block identify the color of each upper-half main bearing, while letters marked on the front end of the crankshaft indicate the color of each lower half main bearing.