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Home >> Geo >> 1990 >> Metro Base, 4D Hatchback, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 15 (1.0L 3-CYL - VIN [5] & 1.0L 3-CYL Turbo - VIN [2]) >> Overhaul >> Main Bearings Service >> Standard Bearing

Standard Bearing

WARNING: This page is about a different car, the 1988 Chevrolet Sprint. However, it is still accessible from the selected car via links, so may be relevant.
  1. If bearings are damaged or exceed specifications, select a new standard bearing using the following procedure. Locate 4 numbers stamped on crankshaft counterweight of cylinder No. 1. See Fig 1.
  2. The first number (left) indicates journal diameter at No. 1 bearing cap. The second number indicates journal diameter at No. 2 bearing cap. The third number indicates journal diameter at No. 3 bearing cap. The fourth number indicates journal diameter at No. 4 bearing cap. See Fig 1.
    Fig 1: Location of Stamped Numbers on Counterweights
    G80629Courtesy of GENERAL MOTORS CORP.
  3. Measure bearing cap bore diameter without bearing installed. There are 4 letters stamped on oil pan mating surface of cylinder block indicating cap bore diameter. See Fig 2.
  4. Reading from left-to-right, first letter applies to cap No. 1, second letter applies to No. 2 cap, third letter applies to No. 3 cap and the fourth letter applies to the No. 4 cap. Refer to the CRANKSHAFT BEARING JOURNAL BORE  table.
    CRANKSHAFT BEARING JOURNAL BORE

    Letter (1) Cap Diameter: In. (mm)
    A 1.9291-1.9294 (49.000-49.007)
    B 1.9294-1.9296 (49.007-49.012)
    C 1.9296-1.9298 (49.012-49.017)
    (1) Letters only INDICATE cap diameter. Diameter must be measured.
    STANDARD BEARING SELECTION (1)

    Block Letter No. 1 No. 2 No. 3
    A Green Black No Paint
    B Black No Paint Yellow
    C No Paint Yellow Blue
    (1) Numbers refer to crankshaft numbers.
    Fig 2: Location of Stamped Letters on Cylinder Block
    G80051Courtesy of GENERAL MOTORS CORP.
    NOTE: There are 5 sizes of standard bearings. Paint marks are applied for identification purposes. Each color indicates thickness at center of bearing.
  5. From numbers stamped on crankshaft counterweights of cylinder No. 1 and letters stamped on oil pan mating surface, determine new standard size bearing to be installed on each journal.
  6. Use Plastigage method to measure main bearing clearance. If clearance still exceeds specifications, use next size thicker bearing and remeasure. When replacing crankshaft or cylinder block for any reason, select new standard bearings by referring to numbers and letters.
MAIN BEARING IDENTIFICATION

Color Code Bearing Thickness: In. (mm)
Green .0786-.0787 (1.996-2.000)
Black .0787-.0789 (1.999-2.003)
No Paint .0788-.0790 (2.002-2.006)
Yellow .0789-.0791 (2.005-2.009)
Blue .0791-.0792 (2.008-2.012)
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