Standard Bearing Selection

Fig. 49 Installing Main Bearing Caps:

Fig. 50 Measuring Main Bearing Clearance:

Two types of main bearings are available, standard and 0.0098 inch (0.25mm) undersize, and each of them has five kinds of bearings differing in tolerance. Each main bearing cap is stamped with a number and an arrow. When installing bearing cap, arrow must point towards crankshaft pulley side, Fig. 49. Check main bearing clearance as follows:
1. Clean bearings and crankshaft main journals using a suitable solvent.
2. Place a piece of gaging plastic the full width of the bearing (parallel to crankshaft) on journal, avoiding oil passage hole.
3. Install bearing cap and tighten cap bolts to specifications. Do not rotate crankshaft while gaging plastic is installed.
4. Remove bearing cap. Using scale on gaging plastic envelope, measure gaging plastic width at its widest point, Fig. 50.
5. If clearance exceeds .0023 inch, replace bearing. Always replace both upper and lower inserts as a unit. A new standard bearing may produce proper clearance, if not, it will be necessary to regrind crankshaft journal for use of 0.0098 inch undersize bearing. After selecting appropriate bearing, recheck clearance.

If bearing is in malcondition, or bearing clearance is out of specification, select a new standard bearing according to the following procedure.

Fig. 51 Distinguishing Crankshaft Journal Diameters:

Fig. 52 Distinguishing Crankshaft Journal Diameters:

1. Using a suitable micrometer, measure journal diameter. On DOHC models, crank web of No. 1 cylinder has five stamped numbers, Fig. 51. On SOHC models, crank webs of No. 2 and No. 3 cylinder has five stamped numbers, Fig. 52. The three different numbers represent the following journal diameters:
a. No. 1, 1.7714-1.7716 inches.
b. No. 2, 1.7712-1.7714 inches.
c. No. 3, 1.7710-1.7712 inches.
2. The first, second, third, fourth and fifth (intake manifold side to exhaust manifold side on DOHC or left to right on SOHC) stamped numbers on crank web, indicate journal diameters at bearing caps 1, 2, 3, 4 and 5 respectively. For example, the first No. 3 indicates that journal diameter at bearing No. 1 is within 1.7710-1.7712 inches, and second No. 1 indicates that journal diameter at bearing cap No. 2 is within 1.7714-1.7716 inches.

Fig. 53 Distinguishing Cap Bore Diameters:

3. Using a suitable micrometer, check bearing cap bore without bearing. There are five letters stamped on mating surface of cylinder block, Fig. 53. These letters represents cap bore diameters as follows:
a. Letter A, 1.9292-1.9294 inches.
b. Letter B, 1.9294-1.9296 inches.
c. Letter C, 1.9296-1.9298 inches.
4. The first, second, third, fourth and fifth (left to right) stamped letters indicate cap bore diameter of bearing caps 1, 2, 3, 4 and 5 respectively, Fig. 53. For example, the first letter B indicates that cap bore diameter of bearing cap No. 1 is within 1.9294-1.9296 inches, and the fifth letter A indicates that cap bore diameter of cap No. 5 is within 1.9292-1.9294 inches.
5. There are five types of standard bearings differing in thickness. Each bearing has a painted identification color on its side. Each color indicates thickness at center of bearing as follows:
a. Green, .0786-.0787 inch.
b. Black, .0787-.0788 inch.
c. Colorless (no paint), .0788-.0789 inch.
d. Yellow, .0789-.0790 inch.
e. Blue, .0790-.0791 inch.

Fig. 54 Standard Bearing Chart:

6. From the number stamped on crank web, Fig. 51 and 52, and the letters stamped on surface of cylinder block, Fig. 53, determine new standard bearing to be installed to journal, by referring to table, Fig. 54. For example, if number stamped on crank web is 3 and letter stamped on cylinder block is B, install new standard bearing with a Yellow painted identification mark.
7. Using gaging plastic, check bearing clearance with new standard bearing selected. If clearance exceeds limits, use next thicker bearing and recheck clearance.
8. If replacing crankshaft or cylinder block, select new standard bearings by numbers stamped on new crankshaft or letters stamped on cylinder surface.