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Home >> GMC >> 2006 >> Sierra 1500 HD, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1670 (Engine Mechanical - 4.8L, 5.3L, 6.0L, 6.2L - Repair Instructions - Off Vehicle (2 Of 3)) >> Valve Guide Reaming, and Valve and Seat Grinding >> Valve Guide Reaming

Valve Guide Reaming

WARNING: This page is about a different car, the 2010 GMC Sierra, 2010 GMC Cab & Chassis Sierra, 2010 Chevrolet Silverado, and 2010 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
    Fig 1: Measuring Valve Stem-To-Guide Clearance
    GM65822Courtesy of GENERAL MOTORS CORP.
    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.
  1. Using the J 8001:  dial indicator, measure the valve stem-to-guide clearance. 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 gauge to measure the guide bore.

    2. Fig 2: Inspecting For Excessive Valve Stem To Guide Clearance
    GM156172Courtesy of GENERAL MOTORS CORP.
  2. If the clearance measurement between the valve stem (1) and guide (2) is not within specification, the valve and/or the cylinder head must be replaced. Refer to Engine Mechanical Specifications (RPO L20 VIN A) or Engine Mechanical Specifications (RPO L96 VIN G) or Engine Mechanical Specifications (RPO L9H) or Engine Mechanical Specifications (RPO LC9 VIN 3) or Engine Mechanical Specifications (RPO LMG VIN 0) or Engine Mechanical Specifications (RPO LY6 VIN K) .
    3. Fig 3: Identifying Valve 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.
    • 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 (RPO L20 VIN A) or Engine Mechanical Specifications (RPO L96 VIN G) or Engine Mechanical Specifications (RPO L9H) or Engine Mechanical Specifications (RPO LC9 VIN 3) or Engine Mechanical Specifications (RPO LMG VIN 0) or Engine Mechanical Specifications (RPO LY6 VIN K) .

    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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