Bearing - Clearance
BEARING CLEARANCEUse either of the following two methods, however, method "A" gives more reliable results and is preferable.
Method A (Using bore gauge & micrometer)
Main bearing
1. Set main bearings in their proper positions on cylinder block and main bearing cap.
2. Install main bearing cap and bearing beam to cylinder block. Tighten all bolts in correct order.
3. Measure inner diameters "A" of each main bearing.
4. Measure outer diameters "Dm" of each crankshaft main journal.
5. Calculate main bearing clearance.
Main bearing clearance = A - Dm
Standard: ..............0.035 - 0.045 mm (0.0014 - 0.0018 inch)
Limit: ..............0.065 mm (0.0026 inch)
If it exceeds the limit, replace bearing.
If clearance cannot be adjusted using any standard bearing grade, grind crankshaft journal and use undersized bearing.
a. When grinding crankshaft journal, confirm that "L" dimension in fillet roll is more than the specified limit.
"L": ..............0.1 mm (0.004 inch)
b. Refer to SDS for grinding crankshaft and available service parts.
6. If crankshaft or cylinder block is replaced with a new one, select thickness of main bearings as follows:
a. Grade number of each cylinder block main journal is punched on the respective cylinder block. These numbers are punched in either Arabic or Alphabet. If measured diameter is out of grade punched, decide suitable grade using table in SDS.
b. Grade number of each crankshaft main journal is punched on the respective crankshaft. These numbers are punched in either Arabic or Alphabet. If measured diameter is out of grade punched, decide suitable grade using table in SDS.
Main bearing selection table:
c. Select main bearing with suitable thickness according to the table shown.
Connecting Rod Bearing (Big end)
1. Install connecting rod bearing to connecting rod and cap.
2. Install connecting rod cap to connecting rod. Tighten bolts to the specified torque.
3. Measure inner diameter "C" of connecting rod.
4. Measure outer diameter "Dp" of each crankshaft pin journal.
5. Calculate connecting rod bearing clearance.
Connecting rod bearing clearance = C - Dp
Standard: ...........0.034 - 0.059 mm (0.0013 - 0.0023 inch)
Limit: ...........0.070 mm (0.0028 inch)
6. If it exceeds the limit, replace bearing.
7. If clearance cannot be adjusted within the standard of any bearing, grind crankshaft journal and use undersized bearing.
8. If crankshaft is replaced with a new one, select connecting rod bearing according to the table shown.
Connecting rod bearing grade number (Identification color)::
These numbers are punched in either Arabic or Roman numerals.
Method B (Using plastigage)
CAUTION: Do not turn crankshaft or connecting rod while plastigage is being inserted.
When bearing clearance exceeds the specified limit, ensure that the proper bearing has been installed. If incorrect bearing clearance exists, use a thicker or undersized main bearing to ensure specified clearance.