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CYLINDER BLOCK — Inspection (Cont'd) Main Bearing Clearance and Selection (Supplement-V)

EM-5039prose procedure

NEM298 shows a 5-character grade-code stamp 'A E K Q U' on the crankshaft web for the No. 5 main journal example — one character per main journal No.1 → No.5. The upper (cylinder-block) halfshell is always code B (black); the lower (cap) halfshell is selected per the punched code. Tables referenced in step 8(c) are continued on the following pages.

Continued from EM-5038

Inspection (Cont'd)

Main bearing clearance (continued)

  1. 2
    Install main bearing cap to cylinder block.
    Tighten all bolts in correct order to the specified torque.
  2. 3
    Measure inner diameter of each main bearing.
    Dial bore gauge measuring the inner diameter of an installed main bearing inside the cylinder block / main bearing cap saddle — illustrates Inspection step 3 (measure inner diameter of each main bearing).
    EEM071
  3. 4
    Measure outer diameter of each main journal in crankshaft.
    Hand holding a micrometer measuring the outer diameter of a crankshaft main journal — illustrates Inspection step 4 (measure outer diameter of each main journal).
    SEM506A
  4. 5
    Calculate main bearing clearance. Main bearing clearance = Inner dia. − Outer dia.
    Standard: 0.01 - 0.036 mm (0.0004 - 0.0014 in)
  5. 6
    If it exceeds the standard clearance, replace bearing.
  6. 7
    If clearance cannot be adjusted within the standard of any bearing, grind crankshaft journal and use undersized bearing.
    When grinding crank pin and crank journal:
    a. Grind until clearance is within specified standard bearing clearance.
    b. Refer to S.D.S. for standard bearing clearance and available spare parts.
  7. 8
    If crankshaft, cylinder block or main bearing is reused, measure main bearing clearance. If crankshaft, cylinder block and main bearings are replaced with new ones, it is necessary to select thickness of main bearings as follows:
    a. The code of each cylinder block halfshell is always B (black).
    b. The code of each main bearing cap halfshell is punched on the crankshaft and cylinder block.
    c. Select main bearing with suitable thickness according to the following tables.
    Top: enlarged view of the main bearing grade-code stamping on the crankshaft web for No. 5 main journal — five-character punched code 'A E K Q U' (one letter per main journal, No.1 → No.5). Bottom: cylinder block side view with leader pointing to 'Main journal No. 1 flywheel side'. Used to read out the cap-side halfshell selection codes.
    NEM298
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See also

S.D.S. — Standard bearing clearance and available spare parts

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