Main Bearing Fitting
Crankshaft thrust washers are not selectable and are only available in a single thickness.
The upper and lower main bearings are "select fit" to achieve proper oil clearances. Crankshaft main bearing journal diameter grade markings (1) are stamped into the front crankshaft counterweight. These marks are read from left to right, corresponding with journal number 1, 2, 3, 4.
There are a string of ten (10) digits on the front of the counterweight. The FIRST 6 correspond to the Rod Bearing Sizes. The LAST 4 correspond to the Main Bearing Sizes.
There are times were the human readable pin stamp on the #1 counterweight is difficult to read. If necessary there is another way to obtain the bearing classification from the crankshaft. Using a barcode scanner or a 2D reader APP, available for most Smart phones, scan the 2D Matrix located on the #8 crankshaft counterweight. The last ten of the scanned digits are used in the same manner as the grade markings typically on the #1 counterweight.
Crankshaft main bearing journal diameter grade markings correspond to specific journal diameters. The chart below identifies the five crankshaft grade markings and their associated journal diameters.
| Crankshaft Marking | Journal Size mm (in.) |
|---|---|
| 1 | 67.9870 - 67.9905 mm (2.6766 - 2.6767 in.) |
| 2 | 67.9906 - 67.9941 mm (2.6768 - 2.6769 in.) |
| 3 | 67.9942 - 67.9977 mm (2.6769 - 2.6771 in.) |
| 4 | 67.9978 - 68.0013 mm (2.6771 - 2.6772 in.) |
| 5 | 68.0014 - 68.0050 mm (2.6772 - 2.6773 in.) |
Engine block main bearing journal diameter grade markings (2) are stamped into the left side of the engine block. These marks are read from left to right, corresponding with journal number 1, 2, 3, 4.
Engine block main bearing journal grade markings correspond to specific journal diameters. The chart below identifies the five engine block grade markings and their associated journal diameters.
| Engine Block Marking | Journal Size mm (in.) |
|---|---|
| 1 | 73.0055 - 73.0090 mm (2.8742 - 2.8744 in.) |
| 2 | 73.0019 - 73.0054 mm (2.8741 - 2.8742 in.) |
| 3 | 72.9983 - 73.0018 mm (2.8739 - 2.8741 in.) |
| 4 | 72.9947 - 72.9982 mm (2.8738 - 2.8739 in.) |
| 5 | 72.9910 - 72.9946 mm (2.8736 - 2.8738 in.) |
For upper and lower main bearing selection, obtain the grade identification marks from the crankshaft and engine block. Main bearings are available in five sizes. Upper and lower sizes can be mixed on a journal in order to achieve the desired oil clearance. The chart below identifies the five sizes available and how they should be selected based on crankshaft and engine block grade markings.
| Engine Block Marking | Crankshaft Marking | ||||
| 1 | 2 | 3 | 4 | 5 | |
| 1 | 1/1 | 1/2 | 2/2 | 2/3 | 3/3 |
| 2 | 1/2 | 2/2 | 2/3 | 3/3 | 3/4 |
| 3 | 2/2 | 2/3 | 3/3 | 3/4 | 4/4 |
| 4 | 2/3 | 3/3 | 3/4 | 4/4 | 4/5 |
| 5 | 3/3 | 3/4 | 4/4 | 4/5 | 5/5 |
| UPPER/LOWER Main Bearings to Achieve 0.024 - 0.050 mm (0.0009 - 0.0020 in.) Oil Clearance | |||||
The upper main bearing shell (2) and lower main bearing shell (1) are marked with the bearing size (3) on the bearing lining surface. The upper and lower bearings are available in five different sizes and can be mixed on a journal in order to achieve the proper oil clearance.
Upper and lower main bearing shells are available in five sizes. The chart below identifies the five bearing sizes.
| Bearing Marking | Size mm (in.) |
|---|---|
| 1 | 2.4951 - 2.4987 mm (0.0982 - 0.0984 in.) |
| 2 | 2.4915 - 2.4951 mm (0.0981 - 0.0984 in.) |
| 3 | 2.4879 - 2.4915 mm (0.0979 - 0.0981 in.) |
| 4 | 2.4843 - 2.4879 mm (0.0978 - 0.0979 in.) |
| 5 | 2.4807 - 2.4843 mm (0.0977 - 0.0978 in.) |