Valve Seat

Valve Seats, Refacing

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

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

• Only refaced 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 refacing dimension is still 0 mm or less, replace cylinder head.

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

Refacing 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

Refacing 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