GM Service Manual Online
For 1990-2009 cars only

Special Tools

    • KM-340-1-C Cutter Set
    • KM-571-B Gage or equivalent
    • KM-805 Valve Guide Reamer

Valve Grind - In

    Warning: Refer to Safety Glasses Warning in the Preface section.


    Object Number: 1241253  Size: SH
  1. Lubricate the valve seat using a fine-grained paste.
  2. Lift the valve rhythmically from the seat with a commercially-available valve grinding tool in order to distribute the paste.

  3. Object Number: 1241773  Size: SH
  4. Inspect the contact pattern on the valve head and in the cylinder head.
  5. Clean the valves, the valve guides, and the cylinder head.

Valve Grind

    Warning: Refer to Safety Glasses Warning in the Preface section.

    Important: The valve may be reground only 2 times. Do not grind the valve stem end.


    Object Number: 1241775  Size: SH
  1. Ensure that there are no crater line burns on the valve cone.
  2. Ensure that the angle at the valve face is 45 degrees.
  3. Inspect the assembly height of the intake valves and the exhaust valves.

Valve Guide - Ream

    Warning: Refer to Safety Glasses Warning in the Preface section.


    Object Number: 1241258  Size: SH
  1. Measures the diameter of the valve guide using the KM-571-B  (1) and a commercially available inside micrometer.

  2. Object Number: 1241259  Size: SH

    Important: Valve oversizes may already have been fitted in production.

  3. An oversize service code is on the valve guide and the valve stem end. The Valve Guide Reaming Table gives the correct size, reamer, and production code for each service code. Refer to the Valve Guide Reaming Table in Engine Mechanical Specifications for correct size, reamer, production code, and service code for each service.
  4. Ream the valve guide with the KM-805  (1) from the upper side of the cylinder head to the next oversize.
  5. After reaming, cross out the code and emboss the valve guide with the new code.

Valve Seat - Cut

    Warning: Refer to Safety Glasses Warning in the Preface section.


    Object Number: 1241780  Size: SH
  1. Place the cylinder head on wooden blocks.
  2. Cut the intake and the exhaust valve seats using the KM-340-7 as follows.
  3. Specifications

        • Cut the valve seat to a 45 degree surface (b) with the KM-340-13.
        • Cut the upper correction angle to a 30 degree surface (a) with the KM-340-13.
        • Cut lower correction angle to a 60 degree surface (c) with the KM-340-26.
  4. Clean the chippings from the cylinder head.
  5. Inspect the dimension for the valve seat width.
  6. Specifications

        • The intake valve seat width is 1.2-1.4 mm (0.47-0055 in).
        • The exhaust valve seat width is 1.4-1.8 mm (0.055-0.070 in).
  7. Inspect the assembly height of the intake valves and the exhaust valves. If the specified dimension is exceeded, install new valves. Inspect the assembly height of the intake valves and the exhaust valves again. If the valve assembly height is still too large despite replacing the valves, replace the cylinder head.