Measuring Crankshaft Bearing Clearances

Measuring Crankshaft Bearing Clearances





^ The crankshaft bearings are of the precision insert type and do not use shims for adjustment. If the clearances are excessive, then new upper and lower crankshaft bearings will be required. The service crankshaft bearings are available in the standard size and an undersize.
^ The selective fitting of the crankshaft bearings are necessary in production in order to obtain close tolerances. For this reason, in one journal bore you may use one-half of a standard crankshaft bearing with one-half of an undersize crankshaft bearing.
^ In order to determine the correct replacement bearing size, the bearing clearance must be measured accurately. When checking main bearing clearances, either the micrometer or plastic gage method may be used; however, the micrometer method gives more reliable results and is preferred. When checking connecting rod bearing clearances, the plastic gage method will result in unreliable measurements. The use of J 43690 is preferred.
^ Normally the crankshaft bearing journals wear evenly and are not out-of-round. However, if a crankshaft bearing is being fitted to an out-of-round crankshaft bearing journal, be sure to fit to the maximum diameter of the crankshaft bearing journal. If the crankshaft bearing is fitted to the minimum diameter and the crankshaft bearing journal is excessively out-of-round, the interference between the crankshaft bearing and the crankshaft bearing journal will result in rapid crankshaft bearing failure.
^ If the crankshaft bearing clearance is within specifications, the crankshaft bearing is satisfactory. If the clearance is not within specifications, replace the crankshaft bearing. Always replace both the upper and lower crankshaft bearings as a set.
^ A standard or undersize crankshaft bearing combination may result in the proper clearance. If the proper crankshaft bearing clearance cannot be achieved using the standard or the undersize crankshaft bearings, it may be necessary to repair or replace the crankshaft.

Measuring Crankshaft Bearing Clearances Micrometer Method
1. Measure the crankshaft journal diameter with a micrometer in several places, approximately 90 degrees apart. Average the measurements.
2. Determine the taper and out-of-round of the journal.





3. Install the bearings into the engine block or connecting rod assembly.





4. Install the bearing cap bolts and tighten to specifications.
5. Measure the bearing inside diameter (ID) at two points 90 degrees apart. Average the measurements.
6. In order to determine the bearing clearance, subtract the average journal diameter from the average bearing inside diameter.
7. Compare the readings to specifications.
8. Replace bearing halves as required to obtain the proper bearing clearances.

Measuring Connecting Rod Bearing Clearances - J 43690 Method
1. Remove the oil pan and other necessary components to gain access to the connecting rods. Remove the oil pump, screen, and deflector, when applicable.
2. Rotate the crankshaft until the crankshaft journal/connecting rod to be measured is in the 10 o'clock position.





Important: The crankshaft must be secure with no movement or rotation in order to obtain an accurate reading. Remove an intermediate bearing cap, as required, in order to secure the crankshaft and allow measurement of connecting rod bearing clearances.

3. Remove the bearing cap bolts. cap and bearing half.

Notice: Refer to Fastener Notice in Service Precautions.

4. Insert a piece of paper card stock onto the crankshaft journal. Install the bearing half, bearing cap, and bolts.





5. Install the foot (1) and bolt (2) to the pivot arm assembly (3). Tighten the bolt until snug.





6. Install the screw (1 or 3) to the pivot arm assembly (2).





7. Install the pivot arm assembly (1) onto the connecting rod.





8. Position the foot of the pivot arm assembly over the large end of the connecting rod bolt.
9. Position the screw (1) onto the small end of the connecting rod bolt and tighten securely.





10. Install the base (1) and bolt (2) to the of pan rail.





11. Align the center of the base (1) with the screw (3) of the pivot arm assembly. Tighten the bolt (2) until snug.





12. Align the link (1) of the pivot arm assembly on a plane (3) equal to that of the connecting rod beam (2).





13. With the link of the pivot arm assembly aligned to the beam of the connecting rod, position the pivot arm to the base and insert the pin (1).





14. Insert the handle (1) to the pivot arm assembly.





15. Select the adapter (2), as required, and install to the swivel base (1). Tighten until snug.





Important: The clamp of the swivel base and the shaft of the indicator should be free of oil or other debris. A loose or improperly clamped indicator may indicate incorrect readings.

16. Install the indicator (2) to the swivel base (1). Tighten the clamp of the base until snug.





17. Install the swivel base (1) to the oil pan rail of the engine block. Tighten until snug.





18. Adjust the swivel base as required and position the indicator tip slightly above the connecting rod cap. Lock the swivel base in position by rotating the locking lever (1). Do not allow the tip of the indicator to contact the connecting rod at this time.





19. The tip of the indicator should be positioned above and NOT in contact with the cap end of the connecting rod.





20. Rotate the fine adjustment knobs on the dial indicator end of the swivel base to position the tip of the indicator in contact with the connecting rod.





21. Lightly actuate the handle of the pivot arm assembly, multiple times in both directions, to ensure the oil film is removed from the journal.





22. Load the handle in the forward position and zero the dial indicator. Load the handle multiple times in both directions and record the reading

Important: During this procedure, card stock may enter the crankshaft journal oil galleries. Be sure to remove all card stock from the bearing journal and oil galleries prior to reassembly.

23. Remove the bearing cap bolts, cap, and paper stock.
24. Replace bearing halves as required to obtain the proper bearing clearances.
25. Install the bearings, cap, and bolts.

Measuring Crankshaft Bearing Clearances - Plastic Gage Method





1. Install the crankshaft bearings into the engine block.





2. Install the crankshaft.





3. Install the gaging plastic the full width of the journal.





4. Install the crankshaft bearings into the crankshaft bearing caps.





5. Install the crankshaft bearing caps in the original positions and with the arrow on the crankshaft bearing caps in the direction of the front of the engine block.
6. Install the crankshaft bearing cap bolts.
^ Tighten the crankshaft bearing caps to 105 Nm (77 ft. lbs.).
7. Remove the crankshaft bearing cap bolts.
8. Remove the crankshaft bearing caps. The gaging plastic may adhere to either the crankshaft bearing journal or the crankshaft bearing surface.





9. Without removing the gaging plastic, measure the compressed width at the widest point using the graduated scale on the edge of the gaging plastic envelope.
If the flattened gaging plastic tapers toward the middle or the ends, there may be a difference in clearance indicating taper, low spot or other irregularity of the crankshaft bearing or the crankshaft bearing journal.
10. Remove the flattened gaging plastic.
11. Measure the remaining crankshaft bearing journals.

Measuring Connecting Rod Bearing Side Clearance





1. Insert a feeler gage between the connecting rod caps and measure the connecting rod side clearance. The proper connecting rod side clearance specification is 0.15-0.44 mm (0.006-0.017 inch).
2. Connecting rod side clearances may also be measured with a dial indicator set.