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Home >> Chevrolet >> 2020 >> Express 2500 LS, 6.0L Eng VIN G >> Repair and Diagnosis >> External Pages >> Different car >> Section 3 (Engine Mechanical - 4.3L (LV1)) >> Repair Instructions - Off Vehicle >> Valve Guide Reaming, and Valve and Seat Grinding >> Valve Guide Reaming

Valve Guide Reaming

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  1. GM4087454Courtesy of GENERAL MOTORS COMPANY
    CAUTION:

    Excessive valve stem-to-guide clearance may cause a noisy valve train, premature valve stem oil seal wear, component damage, and/or excessive engine oil consumption.

    CAUTION:

    Insufficient valve stem-to-guide clearance will result in noisy or sticking valves. Valves that are too tight may disturb engine smoothness or lead to component damage.

    Measure the valve stem to guide clearance.

    1. Using a micrometer (1) measure the diameter of the valve stem (a).
    2. Using a ball style measuring gauge, measure the inner diameter (b) of the valve guide at the specified depth. Refer to Engine Mechanical Specifications (L20 VIN A) , or Engine Mechanical Specifications (LC8 VIN B) , or Engine Mechanical Specifications (L96 VIN G) .
    3. Subtract the valve stem diameter (a) from the valve guide inner diameter (b) to obtain the valve stem to guide clearance.
  2. If the clearance measurement between the valve stem and guide is not within specification, the valve and/or the cylinder head must be replaced. Refer to Engine Mechanical Specifications (L20 VIN A) , or Engine Mechanical Specifications (LC8 VIN B) , or Engine Mechanical Specifications (L96 VIN G) .
  3. GM156174Courtesy of GENERAL MOTORS COMPANY

    Inspect the valve stems for excessive scoring, wear, or warpage.

    • A valve stem that has excessive scoring (3 or 4) or wear (4 or 6) must be replaced.
    • If a valve guide is worn or has excessive stem-to-guide clearance, the cylinder head should be replaced.
  4. Measure the valve stem diameter. If the valve stem diameter is not within specification, the valve must be replaced. Refer to Engine Mechanical Specifications (L20 VIN A) , or Engine Mechanical Specifications (LC8 VIN B) , or Engine Mechanical Specifications (L96 VIN G) .

    If the valve stem diameter is within specifications, and the stem-to-guide clearance is excessive, the cylinder head must be replaced.

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