GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1999 🢒 Eldorado 🢒 Engine 🢒 Engine Mechanical - 4.6L 🢒 Valve and Seat Grinding

Valve Cleaning Procedure
  1. Use soft bristle wire brush to clean any carbon build-up from the valve head. DO NOT use a wire brush on any part of the valve stem. The valve stem is chrome plated to provide enhanced wear characteristics. Wire brushing the stem could remove the chrome plating.
  2. Thoroughly clean the valve with solvent and wipe dry.

Valve Visual Inspection Procedure

    Object Number: 156174 Size: SH
  1. Inspect the valve for damage from the head to tip for the following conditions:
    2. • Pitting in the valve seat area (1).
    • Lack of valve margin (2).
    • Bending in the valve stem (3).
    • Pitting or excessive wear in the stem (4).
    • Worn valve key grooves (5).
    • Worn valve tip (6).
  2. Replace the valve if any of these conditions exist.

Valve Measurement and Reconditioning Overview
    • Proper valve service is critical to engine performance. Therefore, all detailed measurement procedures must be followed to identify components that are out of specification.
    • If the measurement procedures reveal that the valve or valve seat must be reconditioned, it is critical to perform the measurement procedures after reconditioning.

Valve Stem Tip Height Measurement Procedure

    Object Number: 71386 Size: SH
  1. Check the valve stem height by measuring the distance from the valve spring seat (the flat metal surface of the valve stem oil seal) to the tip of the valve (1).
  2. Compare your measurements with the following specifications:

    3. Intake Valve Stem Tip Height Specification
    Intake valve: 35.30-36.92 mm (1.389-1.453 in) nominal, 37.17 mm (1.463 in) maximum.

    Exhaust Valve Stem Tip Height Specification
    Exhaust valve: 33.85-35.38 mm (1.332-1.392 in) nominal, 35.63 mm (1.402 in) maximum.

  3. If the maximum height specification is exceeded, the valve must be replaced and the stem height re-measured.
  4. If the stem height with a new valve still exceeds the maximum allowed, the cylinder head must be replaced.

Valve Seat Width Measurement Procedure

    Object Number: 71387 Size: SH
  1. Measure the valve seat width in the cylinder head using a proper scale.

    2. Object Number: 376399 Size: SH
  2. Measure the seat width on the valve face (1) using a proper scale.

    3. Important:  The seat contact area must be at least 0.5 mm (0.020 in) from the outer diameter (margin) of the valve. If the contact area is too close to the margins, the seat must be reconditioned to move the contact area away from the margin.

  3. Compare your measurement with the following specifications:

    4. Intake Valve Seat Width Specification
    Intake valve seat width: 0.450-0.850 mm (0.017-0.033 in)

    Exhaust Valve Seat Width Specification
    Exhaust valve seat width: 0.700-1.100 mm (0.027-0.043 in)

  4. If the seat widths are acceptable, check the valve seat roundness using the Valve Seat Roundness Measurement Procedure.
  5. If the seat width is not acceptable, you must grind the valve seat using the Valve and Seat Reconditioning Procedure to bring the width back into specification. Proper valve seat width is critical to providing the correct amount of valve heat dissipation.

Valve Seat Roundness Measurement Procedure
  1. Measure the valve seat roundness using a dial indicator attached to a tapered pilot installed in the guide. The pilot should have a slight bind when installed in the guide.

    2. Important: A pilot of the correct size must be used. DO NOT attempt to force the pilot into the guide. Pilots with adjustable diameters to fit various size guides are not recommended. Valve guide damage could occur if an adjustable pilot is used.

  2. Compare your measurement with the following specification:

    3. Valve Seat Roundness Specification
    Maximum valve seat roundness: 0.10 mm (0.004 in)

  3. If the valve seat exceeds the roundness specification, you must grind the valve and valve seat using the Valve and Seat Reconditioning Procedure.
  4. If new valves are being used, the valve seat roundness must be within 0.05 mm (0.002 in).

Valve Margin Measurement Procedure

    Object Number: 57502 Size: SH
  1. Measure the valve margin using an appropriate scale.
  2. Reference the specifications in this section for minimum valve margin and compare them to your measurements.
  3. If the valve margins are beyond specification, replace the valves.
  4. If the valve margins are within specification and do not require refacing, test the valve for seat concentricity using the Valve-to-Seat Concentricity Measurement Procedure.

Valve-to-Seat Concentricity Measurement Procedure
    • Checking the valve-to-seat concentricity determines whether the valve and seat are sealing properly.
    • You must measure the valve face and the valve seat to ensure proper valve sealing.

    Object Number: 53234 Size: SH
  1. Coat the valve face lightly with blue dye (3).
  2. Install the valve in the cylinder head.
  3. Turn the valve against the seat with enough pressure to wear off the dye.
  4. Remove the valve from the cylinder head.
  5. Inspect the valve face.
    6. • If the valve face is concentric (providing a proper seal) with the valve stem, a continuous mark will be made around the entire face (1).

       Important: The wear mark MUST be at least 0.5 mm (0.020 in) from the outer diameter (the margin) of the valve. If the wear mark is too close to the margin the seat must be reconditioned to move the contact area away from the margin.

    •  If the face is not concentric with the stem, the mark will NOT be continuous around the valve face and the valve should be refaced or replaced and the seat must be reconditioned using the Valve and Seat Reconditioning Procedure.

Valve and Seat Reconditioning Procedure
    • If the valve seat width, roundness or concentricity is beyond specifications, you must grind the seats in order to ensure proper heat dissipation and prevent the build up of carbon on the seats.
    • It is necessary to reface the valve if seat reconditioning is required unless a new valve is used.

    Object Number: 52037 Size: SH
  1. Grind the valve seats at a 46 degree angle to the proper width. Use 20 and 65 degree grinding stones in order to narrow, raise or lower the seat as necessary.

    2. Intake Valve Seat Width Specification
    Narrow the intake valve seat width to 0.065 mm (0.025 in).

    Exhaust Valve Seat Width Specification
    Narrow the exhaust valve seat width to 0.900 mm (0.035 in)

  2. If you are using the original valve, grind the valve face at a 45 degree angle. Re-measure the valve margin after grinding using the Valve Margin Measurement Procedure. Replace the valve if the margin is out of specification. New valves do not require grinding.
  3. When grinding the valves and seats, grind off as little material as possible. Cutting valve seat results in lowering the valve spring pressure.
  4. Install the valve in the cylinder head.
    5. • If you are using refaced valves, lap the valves into the seats with a fine grinding compound. The refacing and reseating operations should leave the refinished surfaces smooth and true so that minimal lapping is required. Excessive lapping will groove the valve face and prevent a good seat when hot.

       Important: Be sure to clean any remaining lapping compound from the valve and seat with solvent and compressed air prior to final assembly.

    • If you are using new valves, do not lap the valves under any condition.
  5. After obtaining the proper valve seat width in the cylinder head you must re-measure the valve stem height using the Valve Stem Height Measurement Procedure.
  6. If the valve stem height is acceptable, test the seats for concentricity using the Valve-to-Seat Concentricity Measurement Procedure.