50. Valve and Seat Grinding

Cleaning Procedure





1. Use soft bristle wire brush to clean any carbon build-up from the front and backside of the valve head only. DO NOT use a wire brush on any part of the valve stem. Brushing the stem could remove some of the chrome plating that is critical to preventing valve guide wear.
2. Thoroughly clean the valve with solvent and wipe dry.

Visual Inspection
1. Inspect the valve for damage from the head to tip for the following conditions:
^ 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.





3. Inspect the valve head for the following conditions:
^ Lack of valve margin (1)
^ Pitting in the valve seat area (2)
^ Damage to the valve seat (3)
^ Scoring in the valve margin area (4)
4. Replace the valve if any of these conditions exist.

Measuring and Grinding the Valves and Seats





1. Measure the valve seat width in the cylinder head. Refer to Specifications.





2. If the valve seat width is beyond these specifications, you must replace the cylinder head and valves. No valve seat grinding is allowed as this will effectively increase the stem height and upset the relationship to the rest of the valve train components.
3. If the valve seat widths are acceptable, check the valve seat roundness.
4. The roundness should be within 0.050 mm (0.004 inch) total, as measured with a dial indicator and a solid, slightly tapered pilot which has a slight bind in the valve guide when installed.
5. If the valve seats exceed the roundness specification, replace the cylinder head and valves.





6. Measure the valve margin. Refer to Specifications.
7. If the valves are below this specification, replace the valves. If you are replacing the valves, do not lap them into the seats under any condition. If you are not replacing the valves, you must test the seat concentricity to ensure there is a proper seal.





8. To test the valves for seat concentricity and tight sealing using the following procedure:
8.1. Coat the valve face lightly with blue dye (3).
8.2. Turn the valve against the seat.
8.3. If the valve face is concentric with the valve stem, a mark will be made all around the face. If the face is not concentric with the stem, a mark will be made on only one side of the face.
8.4. Coat the valve seat lightly with blue dye.
8.5. Rotate the valve against the seat to determine if the valve seat is concentric with the valve guide and if the valve is seating all the way around.
8.6. If the valve is not seating properly, it must be replaced. Both of these tests are necessary in order to prove that a proper seat is obtained.





9. The final step in servicing the valves is to check the valve stem height in relation to the valve spring seat. Measuring this dimension will indicate if the valve and/or the valve seat is worn causing the valve tip to protrude from the valve guide more than is allowed. If a new valve is required as a result of the visual inspection, it is still necessary to measure the valve stem height as this indicates a worn valve seat.
10. To determine valve stem height, measure the distance from the valve spring seat to the tip of the valve (1). Refer to Specifications.
11. If the maximum height specification is exceeded, the valve must be replaced and the stem height must be measured again.
12. If a new valve is installed and the maximum height is exceeded, the cylinder head must be replaced.