Tools Required

J 8087 Cylinder Bore Gage

1. Clean the crankshaft of the following elements:

•

Oil

•

Sludge

•

Carbon

2. Inspect the crankshaft oil passages for obstructions.
3. Inspect the crankshaft keyway for nicks or wear.
4. Inspect the crankshaft threads.

Important: If cracks, severe gouges or burned spots are found, the crankshaft must be replaced. Slight roughness may be removed with a fine polishing cloth soaked in clean engine oil. Burrs may be removed with a fine oil stone.

5. Inspect the crankshaft bearing journals and the crankshaft thrust surfaces for the following conditions:

•

Cracks

•

Chips

•

Gouges

•

Roughness

•

Grooves

•	Overheating, discoloration

6. Inspect the corresponding crankshaft bearings for embedded foreign material and determine the source.

Important: Note the location of the crankshaft main bearing high spots. If they are not in line, the crankshaft is bent and must be replaced.

7. Inspect the crankshaft bearings for uneven side-to-side wear. This may indicate a bent crankshaft or a tapered bearing journal.




Important: The crankshaft bearings are the precision insert type. The crankshaft bearings are available in standard and various undersizes.

8. Inspect the outer surfaces of the crankshaft bearings for the following conditions:

•	Wear - surface wear indicates either movement of the insert or high spots in the surrounding material, spot wear.

•	Overheating or discoloration

•	Looseness or rotation indicated by flattened tangs and wear grooves

9. Inspect the thrust surfaces of the main thrust bearing for the following conditions:

•

Wear

•	Grooving, grooves are caused by irregularities of the crankshaft thrust surface.





Important: If crankshaft bearing failure is due to other than normal wear, investigate the cause. Inspect the crankshaft or connecting rod bearing bores.

10. Using the J 8087 inspect the connecting rod bearing bores or crankshaft main bearing bores using the following procedure:

10.1.

Tighten the bearing cap to specification.

10.2.

Measure the bearing bore using J 8087 for taper and out-of-round.

10.3.

No taper or out-of-round should exist.

Bearing Selection

Measure the bearing clearance to determine the correct replacement bearing insert size. There are two methods to measure bearing clearance. Method A gives more reliable results and is preferred.

Method A

Important: Do not mix inserts of different nominal size in the same bearing bore.

1. Measure the crankshaft bearing journal diameter with a micrometer in several places, 90 degrees apart. Average the measurements.
2. Measure the crankshaft bearing journal taper and runout.
3. Install the crankshaft bearing inserts. Tighten the bearing cap bolts to specification.
4. Measure the connecting rod inside diameter in the same direction as the length of the rod with an inside micrometer.
5. Measure the crankshaft main bearing inside diameter with an inside micrometer.
6. Select a set of bearing inserts that will produce the desired clearance.
7. If the specified clearances cannot be met, the crankshaft journals must be reconditioned and undersized bearing inserts installed.

Method B

Important: Do not mix inserts of different nominal size in the same bearing bore.

1. Clean the used bearing inserts.
2. Install the used bearing inserts.
3. Place a piece of gaging plastic across the entire bearing width.
4. Install the bearing caps.

Notice: In order to prevent the possibility of cylinder block or crankshaft bearing cap damage, the crankshaft bearing caps are tapped into the cylinder block cavity using a brass, lead, or a leather mallet before the attaching bolts are installed. Do not use attaching bolts to pull the crankshaft bearing caps into the seats. Failure to use this process may damage a cylinder block or a bearing cap.

5. Install the bearing cap bolts to specification.

Important: Do not rotate the crankshaft.

6. Remove the bearing cap, leaving the gaging plastic in place. It does not matter whether the gaging plastic adheres to the journal or to the bearing cap.
7. Measure the gaging plastic at its widest point with the scale printed on the gaging plastic package.
8. Remove the gaging plastic.
9. Select a set of bearing inserts that will produce the desired clearance.