Standard Procedure - Main Bearing Identification And Selection
The upper and lower main bearings are "select fit" to achieve proper oil clearances. Crankshaft main bearing journal diameter grade markings are stamped into the rear of the crankshaft. These marks are read from right to left, corresponding with journal number 1, 2, 3, 4, 5.
Crankshaft main bearing journal diameter grade markings correspond to specific journal diameters. The chart below identifies the 19 crankshaft grade markings and their associated journal diameters.
| Crankshaft Marking | Journal Size mm (in.) | Crankshaft Marking | Journal Size mm (in.) |
|---|---|---|---|
| A | 48.000 mm (1.8898 in.) | M | 47.990 mm (1.8894 in.) |
| B | 47.999 mm (1.8897 in.) | N | 47.989 mm (1.8893 in.) |
| C | 47.998 mm (1.8897 in.) | P | 47.988 mm (1.8893 in.) |
| D | 47.997 mm (1.8896 in.) | R | 47.987 mm (1.8892 in.) |
| E | 47.996 mm (1.8896 in.) | S | 47.986 mm (1.8892 in.) |
| F | 47.995 mm (1.8896 in.) | T | 47.985 mm (1.8892 in.) |
| G | 47.994 mm (1.8895 in.) | U | 47.984 mm (1.8891 in.) |
| H | 47.993 mm (1.8895 in.) | V | 47.983 mm (1.8891 in.) |
| K | 47.992 mm (1.8894 in.) | W | 47.982 mm (1.8890 in.) |
| L | 47.991 mm (1.8894 in.) | - | - |
Engine block main bearing bore diameter grade markings are stamped into the right side of the engine block. These marks are read from front to rear, corresponding with journal number 1, 2, 3, 4, 5.
Engine block main bearing bore grade markings correspond to specific bore diameters. The chart below identifies the 14 engine block grade markings and their associated bore diameters.
| Engine Block Marking | Bore Size mm (in.) | Engine Block Marking | Bore Size mm (in.) |
|---|---|---|---|
| A | 51.705 mm (2.0356 in.) | H | 51.712 mm (2.0359 in.) |
| B | 51.706 mm (2.0357 in.) | K | 51.713 mm (2.0359 in.) |
| C | 51.707 mm (2.0357 in.) | L | 51.714 mm (2.0360 in.) |
| D | 51.708 mm (2.0357 in.) | M | 51.715 mm (2.0360 in.) |
| E | 51.709 mm (2.0358 in.) | N | 51.716 mm (2.0361 in.) |
| F | 51.710 mm (2.0358 in.) | P | 51.717 mm (2.0361 in.) |
| G | 51.711 mm (2.0359 in.) | R | 51.718 mm (2.0361 in.) |
For upper and lower main bearing selection, obtain the grade identification marks from the crankshaft and engine block. Main bearings are available in three sizes (red, blue, yellow). Upper and lower sizes can be mixed on a journal in order to achieve the desired oil clearance. The chart below identifies the three sizes available and how they should be selected based on crankshaft and engine block grade markings.
| Crankshaft Marking | Engine Block Marking | |||||||||||||
| A | B | C | D | E | F | G | H | K | L | M | N | P | R | |
| A | R/R | R/R | R/R | R/R | R/R | R/R | R/R | R/B | R/B | R/B | R/B | R/B | R/B | R/B |
| B | R/R | R/R | R/R | R/R | R/R | R/R | R/B | R/B | R/B | R/B | R/B | R/B | R/B | B/B |
| C | R/R | R/R | R/R | R/R | R/R | R/B | R/B | R/B | R/B | R/B | R/B | R/B | B/B | B/B |
| D | R/R | R/R | R/R | R/R | R/B | R/B | R/B | R/B | R/B | R/B | R/B | B/B | B/B | B/B |
| E | R/R | R/R | R/R | R/B | R/B | R/B | R/B | R/B | R/B | R/B | B/B | B/B | B/B | B/B |
| F | R/R | R/R | R/B | R/B | R/B | R/B | R/B | R/B | R/B | B/B | B/B | B/B | B/B | B/B |
| G | R/R | R/B | R/B | R/B | R/B | R/B | R/B | R/B | B/B | B/B | B/B | B/B | B/B | B/Y |
| H | R/B | R/B | R/B | R/B | R/B | R/B | R/B | B/B | B/B | B/B | B/B | B/B | B/Y | B/Y |
| K | R/B | R/B | R/B | R/B | R/B | R/B | B/B | B/B | B/B | B/B | B/B | B/Y | B/Y | B/Y |
| L | R/B | R/B | R/B | R/B | R/B | B/B | B/B | B/B | B/B | B/B | B/Y | B/Y | B/Y | B/Y |
| M | R/B | R/B | R/B | R/B | B/B | B/B | B/B | B/B | B/B | B/Y | B/Y | B/Y | B/Y | B/Y |
| N | R/B | R/B | R/B | B/B | B/B | B/B | B/B | B/B | B/Y | B/Y | B/Y | B/Y | B/Y | Y/Y |
| P | R/B | R/B | B/B | B/B | B/B | B/B | B/B | B/Y | B/Y | B/Y | B/Y | B/Y | Y/Y | Y/Y |
| R | R/B | B/B | B/B | B/B | B/B | B/B | B/Y | B/Y | B/Y | B/Y | B/Y | Y/Y | Y/Y | Y/Y |
| S | B/B | B/B | B/B | B/B | B/B | B/Y | B/Y | B/Y | B/Y | B/Y | Y/Y | Y/Y | Y/Y | Y/Y |
| T | B/B | B/B | B/B | B/B | B/Y | B/Y | B/Y | B/Y | B/Y | Y/Y | Y/Y | Y/Y | Y/Y | Y/Y |
| U | B/B | B/B | B/B | B/Y | B/Y | B/Y | B/Y | B/Y | Y/Y | Y/Y | Y/Y | Y/Y | Y/Y | Y/Y |
| V | B/B | B/B | B/Y | B/Y | B/Y | B/Y | B/Y | Y/Y | Y/Y | Y/Y | Y/Y | Y/Y | Y/Y | Y/Y |
| W | B/B | B/Y | B/Y | B/Y | B/Y | B/Y | Y/Y | Y/Y | Y/Y | Y/Y | Y/Y | Y/Y | Y/Y | Y/Y |
| R=RED B=BLUE Y=YELLOW UPPER/LOWER Main Bearings to Achieve 0.025 - 0.040 mm (0.0010 - 0.0016 in.) Oil Clearance |
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The main bearing shells are color coded (1) on the edge of the bearing. The bearings are available in three different sizes and can be mixed on a journal in order to achieve the proper oil clearance.
Main bearing shells are available in three sizes. The chart below identifies the three bearing sizes.
| Bearing Marking | Size mm (in.) |
|---|---|
| RED | 1.838 mm (0.0724 in.) |
| BLUE | 1.845 mm (0.0726 in.) |
| YELLOW | 1.850 mm (0.0728 in.) |