Crankshaft Main Bearing: Description and Operation

Crankshaft Main Bearing Shell Selection Chart





The axes on the chart refer to:
X1 - Crankshaft Block.
Y1 - Crankshaft Journal Diameter.

The number in each diagonal band represents a PAIR of color coded main bearing shells, which must be used with a specific journal, depending on the combination of journal diameter and crankshaft bore diameter. The color codes for each band are as follows:
1: Blue/Green and Blue,
2: Blue/Green and Blue
3: Blue and Blue.
4: Blue and Green.
5: Green and Green.
6: Green and Yellow
7: Yellow and Yellow.

Consider crankshaft journal 5 (from the example grade markings on the cylinder block) - the cylinder block bore is Grade N and the crankshaft journal diameter is Grade L. From the chart, it will be seen that the point of intersection is in Band 4, which equates to one Blue shell and one Green shell.

When the appropriate pair of color codes have been selected for a journal, either color may be installed to the cylinder block or to the bedplate, but, the shell, which is to be installed to the cylinder block, must have an oil groove and the shell, which is to be installed to the bedplate must be plain.