Crankshaft Main Bearing: Service and Repair
STANDARD PROCEDURE - CRANKSHAFT MAIN BEARING FITTINGThe main bearings are a "select fit" to achieve proper oil clearances. For main bearing selection, the block and crankshaft have grade identification marks.
The marks for the cylinder block main bore grade are located on the left side pan rail (Fig. 81). These grade marks (1, 2, or 3) are read left to right, corresponding to main bore 1, 2, 3, 4.
The grade marks for the crankshaft are located on the rearmost crankshaft counter weight as shown in (Fig. 82). The crankshaft journal grade marks (A, B. or C) are read left to right, corresponding with journal number 1, 2, 3, 4.
Refer to the MAIN BEARING SELECTION CHART to properly select the main bearings. For an example, if the main bore grade is 3 and the journal grade is B. the proper select fit bearing would be a +0.003 mm (+0.0002 inch).
NOTE: Service main bearings have a number from (1-5) marked in ink on the bearing surface (Fig. 83). For verification, refer to the MAIN BEARING SELECTION CHART for number to size identification.
The upper main bearing has a oil feed hole and a center groove to allow lubrication of the main journal and must be properly positioned in the block.
MAIN BEARING SELECTION CHART
REMOVAL
Bearing caps are not interchangeable and are marked to insure correct assembly (Fig. 84). Upper and lower bearing halves are NOT interchangeable.
1. Remove oil pan.
2. Remove oil pick-up tube and windage tray.
3. Identify bearing caps before removal (Fig. 84).
4. Remove bearing caps one at a time. Remove upper half of bearing by inserting Special Main Bearing Tool C-3059 (Fig. 85) into the oil hole of crankshaft.
5. Slowly rotate crankshaft clockwise, forcing out upper half of bearing shell.
INSTALLATION
Bearing caps are not interchangeable and are marked to insure correct assembly. Upper and lower bearing halves are NOT interchangeable (Fig. 86).
CAUTION: Main bearings are select fit.
NOTE: Only one main bearing should be selectively fitted while all other main bearing caps are properly tightened.
When installing a new upper bearing shell, slightly chamfer the sharp edges from the plain side.
1. Lubricate main bearing with clean engine oil.
2. Start bearing in place, and insert Main Bearing Tool C-3059 into oil hole of crankshaft (Fig. 85).
3. Slowly rotate crankshaft counterclockwise sliding the bearing into position. Remove Special Main Bearing Tool C-3059.
NOTE: Lubricate main bearing cap bolts with engine oil before installation.
4. Lubricate and install lower bearing half and main cap Tighten bolts finger tight.
5. For installing thrust washers at the No. 2 main bearing location, use the following procedure:
a. Move crankshaft forward to limit of travel.
Lubricate and install the front thrust washer by rolling the washer onto the machined shelf between the No. 2 upper main bulk head and crankshaft thrust surface (Fig. 87).
b. Move crankshaft rearward to limit of travel.
Lubricate and install the rear thrust washer by rolling the washer onto the machined shelf between the No. 2 upper main bulk head and crankshaft thrust surface.
The main bearing cap bolts must be tightened in the proper sequence. First the inner main cap bolts, secondly the windage tray bolts, lastly the main cap tie (horizontal) bolts.
6. Install each main bearing cap and tighten inner bolts finger tight.
7. Tighten inner main bearing cap bolts to 20 Nm + 1/4 turn (15 ft. lbs. + 1/4 turn).
8. Measure crankshaft end play.
9. Install windage tray. Lubricate bolts with engine oil and tighten to 27 Nm + 1/4 turn (20 ft. lbs. + 1/4 turn).
10. Install the main cap tie (horizontal) bolts and tighten to 28 Nm (250 inch lbs.).
11. Install oil pick-up tube.
12. Install oil pan.
13. Fill engine crankcase with proper oil to correct level.