G 2500 3/4 Ton Van V6-262 4.3L VIN Z (1992)
EXAMPLE 2:
The lower insert is stamped STD (standard) and the upper is stamped 0.0010". The undersize for a STD bearing is 0. Divide 0 by 2 to get 0.
Divide 0.0010" by 2 to get 0.0005". Add 0 and 0.0005" together to calculate the bearing undersize, which is 0.0005" in this case.
13.
Add the original bearing undersize calculated in step 12 to the clearance measured and written down in step 9. For example, if a clearance of
0.0030" was measured with plastigage in step 9 and the calculated bearing undersize from step 12 was 0.0005", the bearing clearance for that
particular main journal is equal to 0.0030" plus 0.0005". The bearing clearance would be 0.0035" in this case.
14.
Determine which of the combinations of two sizes of replacement bearings will produce the desired clearance. The two sizes available are 0.001"
and 0.002". One insert of each size may be combined to produce an intermediate undersize of 0.0015". Subtract the replacement bearing size from
the actual clearance to determine which bearing should be used. The bearing that should be used is the one which gives a clearance closer to
0.0008" than to 0.0028". The clearance must not be less than 0.0008". Using the example from step 11, the actual clearance is 0.0035".
Subtracting 0.001" from 0.0035" will give a clearance of 0.0025", just barely within the required range. Subtracting 0.002" from 0.0035" will give
a clearance of 0.0015". The 0.002" undersize bearing set would be the one to use in this case since it gives a clearance closer to 0.0008", but not
less.
15.
Install the replacement upper main bearing insert using tool J 8080.
16.
Install the replacement lower main bearing insert in the main bearing cap. Lay a piece of plastigage across the width of the lower main bearing
insert (same as step 5).
17.
Repeat steps 7, 8 and 9.
18.
Measuring the plastigage with the scale on the envelope, verify the clearance of the replacement bearings is within the range of 0.001" to 0.003".
19.
Repeat steps 4 through 16 for each main bearing.
20.
Thrust the crankshaft forward and backward several times to seat the thrust bearing.
21.
Reinstall oil pump; torque to 88 N.m (65 lb ft).
22.
Reinstall the oil pan and other hardware.
23.
Before starting the engine, remove the fuel pump fuse and crank the engine until oil pressure registers on the gauge. Stop cranking, let the starter
cool down, then crank for another 15 seconds.
24.
Install fuel pump fuse, start engine, check for leaks or unusual noises.
25.
Road test vehicle, check for leaks or unusual noises.
THE FOLLOWING PROCEDURE IS TO BE USED FOR VEHICLES REQUIRING MAIN BEARING REPLACEMENT WITH THE ENGINE OUT
OF THE VEHICLE
Recommended for K, S and T vehicles.
1.
Remove the engine from the vehicle using the appropriate service manual procedure.
2.
Mount the engine on an engine stand, flip the engine so the oil pan is facing up.
3.
Remove the oil pan.
4.
Remove the oil pump and shield.
5.
Remove the dipstick tube.
6.
Remove one (1) main bearing cap (must do one at a time).
7.
Plasti-gage bearing.
8.
If the bearing clearance is out of specification (clearance greater than 0.003 inches), remove upper main bearing from the block.
9.
Check the size of the original bearing.
10.
Determine what combination of new bearings are required to get the clearance in the acceptable range of 0.0008 inches to 0.0028 inches. See steps
