Inlet valve seat
Exhaust valve seat
Valve dimensions
Valve seats with signs of wear or combustion effects may be remachined as long as the maximum allowable remachining is maintained. If this dimension is exceeded, then the hydraulic lash adjuster in the valve drive ceases to perform its functions. In this case, the cylinder head must be replaced. Valve seats are always finished in such a way as to ensure a flawless appearance of the working surface. Valve seats can be repaired with normal workshop tools. Reamers are required for finishing. Since the handling of these tools requires a certain skill, the work should be done in a workshop.
Warning: Outlet seats are provided with an additional taper. When processing, be sure to pay attention not to damage the constriction radius.
Determining the maximum allowable rework size
1. Insert the valve and press firmly against the seat.
2. Measure the distance - a - between the end of the valve stem and the plane of the contact surface of the cylinder head.
3. The minimum allowable distance values are a (see table).
In order to obtain the maximum allowable reworking size, it is necessary to subtract its minimum allowable value from the measured distance - a -.
So:
(E mm = measured distance - a) = (E mm = minimum allowable distance value - a) = (E mm = maximum allowable reworking size (b)).
The minimum allowable distance values are a
Engine | Inlet valve | Exhaust valve |
2.8 l (30 valves)
|
32.2 mm1)
|
33.0 mm
|
2.6/ 2.8 l (12 valves)
|
33.8mm
|
34.1 mm
|
1) Middle intake valve: 33.2mm
Valve seat angle and width
Engine | Inlet valve | Exhaust valve |
a =
|
39.2 mm (/)
|
32.4mm (/)
|
c =
|
2.0mm
|
2.4mm
|
b - the maximum allowable size of reprocessing (calculated)
Z - lower contact surface of the cylinder head
300 - upper correction angle
450 - valve seat bevel angle
6-cylinder petrol engine: a = max. 3.5mm; b = min. 0.5 mm; a = 450.
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