Valve Seat Measurement
Measure
- Measure the valve seat (1) width in the cylinder head using a scale (2).
- Measure the seat width on the valve face (1) using a correct scale.
Important: The seat contact area must be at least 0.5 mm 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.
- If the seat widths are acceptable, check the valve seat roundness.
- If the seat width is not acceptable, grind the valve seat to bring the width back to specification. Correct valve seat width is critical to providing the correct amount of valve heat dissipation.
- 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.
Important: The correct size pilot must be used. Do not use adjustable diameter pilots. Adjustable pilots may damage the valve guides.
- If the valve seat exceeds the roundness specification, grind the valve and valve seat.
- If new valves are being used, the valve seat roundness must be within 0.05 mm.