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Home >> GMC >> 2005 >> Sierra 1500 HD, 4WD >> Repair and Diagnosis >> Engine Mechanical >> Mechanical >> Engine Mechanical - 4.8L, 5.3L & 6.0L (Repair Instructions - 2 Of 3) >> Off-Vehicle Repair Instructions - Part 2 >> Valve Guide Reaming/Valve and Seat Grinding >> Valve Guide Reaming

Valve Guide Reaming

    Fig 1: Measuring Valve Stem-To-Guide Clearance
    GM65822Courtesy of GENERAL MOTORS CORP.
    IMPORTANT:
    • 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.
    • 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.
  1. Measure the valve stem-to-guide clearance using a dial indicator. Position the tip of the dial indicator at the top of the valve guide.

    Valve stem-to-guide clearance may also be obtained by using a micrometer to measure the valve stem diameter and a ball type measuring gage to measure the guide bore.

    2. Fig 2: Inspecting For Excessive Valve Stem To Guide Clearance
    GM156172Courtesy of GENERAL MOTORS CORP.
  2. A valve stem (1) and guide (2) with excessive clearance must be replaced or the components replaced.

    Refer to Engine Mechanical Specifications (LR4 VIN V) or Engine Mechanical Specifications (LM7 VIN T) or Engine Mechanical Specifications (L33 VIN B) or Engine Mechanical Specifications (L59 VIN Z) or Engine Mechanical Specifications (LQ4 VIN U) or Engine Mechanical Specifications (LQ9 VIN N) .

    3. Fig 3: Identifying Inspection Points For Valves Damage
    GM156174Courtesy of GENERAL MOTORS CORP.
  3. 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.
    • A valve guide that is worn and has excessive stem-to-guide clearance should be reamed and valves with oversize stems installed.
  4. Measure the valve stem diameter. A valve stem with a diameter less than 7.95 mm (0.313 in) must be replaced.

    If the valve stem diameter is within specifications, and the stem-to-guide clearance is excessive, the valve guide must be reamed oversize and a valve with oversize stem installed.

    5. Fig 4: Reaming Valve Guide Using J 37378-1
    GM572270Courtesy of GENERAL MOTORS CORP.
  5. Ream the valve guide using the J 37378-1  . See Special Tools .
  6. Clean the guide bore of all metal shavings and debris.
    7. Fig 5: View Of Valve & Cylinder Head
    GM1272857Courtesy of GENERAL MOTORS CORP.
  7. Install the valve (227-228), with oversize stem, into the cylinder head (218).
  8. Inspect the valve for the proper fit.

    Move the valve back and forth in the guide. The valve should move freely with no resistance or drag.

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