Valve Seat

Valve Seats, Reworking

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

Special tools, testers and auxiliary items required

• Depth gauge

• Valve seat refacing tool

• When repairing engines with leaking valves, it is not sufficient to rework or replace valve seats and valves. It is particularly important to check valve guides for wear on engines with higher mileage. Refer to => [ Valve Guides, Checking ] Testing and Inspection

• Only reface valve seats enough until a perfect contact pattern is obtained.

• Before refacing, determine maximum refacing dimension.

• If refaced dimension is exceeded, hydraulic valve lifter function is no longer guaranteed and cylinder head must be replaced.

Determining maximum allowable refacing dimension

- Insert valve and press it firmly against the valve seat.

• If the valve is to be replaced as part of a repair, use a new valve for the calculation.

- Measure distance - a - between end of valve stem and camshaft center axle (camshaft center axle is located at the level of cylinder head upper edge).





- Calculate the maximum permissible refacing dimension from the measured distance and the minimum dimension.





Measured distance minus minimum dimension = max. permissible refaced dimension.





• If the maximum allowed refaced dimension is 0 mm or less than 0 mm, repeat measurement using new valve. If measurement result is still 0 mm or less than 0 mm, replace cylinder head.

Valve Seats, Reworking





Intake valve seat

a Dia. 26.6 mm
b Approximately 1.0 mm
Z Lower edge of cylinder head
alpha 45° valve seat angle
β 30° upper correction angle
γ 60° lower correction angle

Exhaust valve seat

a Dia. 26.0 mm
b Approximately 1.0 mm
Z Lower edge of cylinder head
alpha 45° valve seat angle
β 30° upper correction angle
γ 60° lower correction angle

• Determining maximum allowable refacing dimension.