Crankshaft Main Bearing: Application and ID
MAIN BEARINGS
GENERAL INFORMATION
- Service main bearings are available in standard size and 0.25 mm (0.0098 inch) undersize, and each of them has 5 kinds of bearings differing in tolerance.
- Upper half of bearing has oil groove as shown in figure. Install this half with oil groove to cylinder block.
- On each main bearing cap, arrow mark and number are embossed as shown in figure.
When installing each bearing cap to cylinder block, point arrow mark toward crankshaft pulley side and install each cap from that side to flywheel side in ascending order of numbers " 1", "2", "3", "4" and "5". Tighten cap bolts to specified torque.
SELECTION OF MAIN BEARINGS
STANDARD BEARING:
If bearing is in malcondition, or bearing clearance is out of specification, select a new standard bearing according to following procedure and install it.
1. First check journal diameter by using following procedure. As shown in figure, crank webs of No.2 and No.3 cylinders have five stamped numerals.
Three kinds of numerals ("1", "2" and "3") represent following journal diameters.
The first, second, third, fourth and fifth (left to right) stamped numerals represent journal diameters at bearing caps "1", "2", "3", "4" and "5" respectively.
For example, in figure, the first (leftmost) numeral "3" indicates that journal diameter at bearing cap "1" is within 51.982 - 51.988 mm, and second one "1" indicate that journal diameter at cap "2" is within 51.994 - 52.000 mm.
2. Next, check bearing cap bore diameter without bearing. On mating surface of cylinder block, four alphabets are stamped as shown in figure.
Three kinds of alphabets ("A", "B" and "C") represent following cap bore diameters.
The first, second, third' fourth and fifth (left to right) stamped alphabets represent cap bore diameters of bearing caps "1", "2", "3", "4", and "5", respectively.
For example, in figure, the first (left most) alphabet "B" indicates that cap bore diameter of bearing cap "1" is within 56.006 - 56.012 mm, and the fifth (right most) alphabet "A" indicates that cap bore diameter of cap n5n is within 56.000 - 56.006 mm.
3. There are five kinds of standard bearings differing in thickness. To distinguish them, they are painted in following colors at the position as indicated in figure.
Each color indicates following thickness at the center of bearing.
4. From numerals stamped on crank webs of No.2 and No.3 cylinders and the alphabets stamped on mating surface of cylinder block, determine new standard bearing to be installed to journal, by referring to table given.
For example, if numeral stamped on crank web is "1" and alphabet stamped on mating surface is "B", install a new standard bearing painted in "Black" to its journal.
5. Using gaging plastic, check bearing clearance with newly selected standard bearing. If clearance still exceeds its limit, use next thicker bearing and recheck clearance.
6. When replacing crankshaft or cylinder block due to any reason, select new standard bearings to be installed by referring to numerals stamped on new crankshaft or alphabets stamped on mating surface of new cylinder block.
UNDERSIZE BEARING (0.25 mm):
- 0.25 mm undersize bearing is available, in five kinds varying in thickness.
To distinguish them, each bearing is painted in following colors at such position as indicated in figure.
Each color represents following thicknesses at the center of bearing.
- If necessary, regrind crankshaft journal and select under size bearing to use with it as follows.
1. Regrind journal to following finished diameter.
Finished diameter: 51.732 - 51.750 mm (2.0367 - 2.0373 inch)
2. Using micrometer, measure reground journal diameter. Measurement should be taken in two directions perpendicular to each other in order to check for out-of-round.
3. Using journal diameter measured above and alphabets stamped on mating surface of cylinder block, select an undersize bearing by referring to table. Check bearing clearance with newly selected undersize bearing.