Valve Seat

Valve Seats, Reworking Dimensions

If a perfect contact pattern is not achieved by grinding the valve seats, rework them.

• If an engine with leaking valves is serviced, reworking or replacing valve seats and valves is not sufficient. The valve guides must be checked for wear, especially on engines with high mileage => [ Valve Guides, Checking ] Testing and Inspection.

• Only rework valve seats enough to achieve a suitable contact pattern.

• Calculate maximum permissible reworking dimension before reworking valve seats.

Special tools, testers and auxiliary items required

• Depth gauge

• Valve seat reworking device

Determining Maximum Allowable Reworking Dimension

• If valve is replaced during repair, use new valve for measurement.

- Insert valve and press firmly against seat.

- Using depth gauge, measure distance - a - between end of valve stem and upper cylinder head surface.





- Determine maximum allowable refacing dimension using distance measured and minimum dimension.

Measured distance minus minimum dimension = maximum permissible refaced dimension.











- If the maximum permissible refacing dimension is 0 mm or less, repeat measurement using new valve.

- If maximum permissible reworking dimension is still 0 mm or less, replace cylinder head.

• If reworking dimension is too small, hydraulic valve clearance compensation will not function properly.

Reworking Intake Valve Seat





a Dia. 30.6 mm
b Maximum permissible reworking dimension.
c 0.9 to 1.5 mm
d Maximum dia. 35.0 mm
r2 Radius 2.0 mm
Z Cylinder head lower edge
alpha 45° valve seat angle
beta 30° upper correction angle
gamma 60° lower correction angle

Reworking Exhaust Valve Seat





a Dia. 26.7 mm
b Maximum permissible reworking dimension.
c 1.2 to 1.7 mm
d Maximum dia. 29.0 mm
r2 Radius 2.0 mm
Z Cylinder head lower edge
alpha 45° valve seat angle
beta 30° upper correction angle
gamma 60° lower correction angle