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Cylinder head: removing and fitting > < Crankshaft dimensions

Leon Mk1

Valve seating: refitting
Valve seating: refitting
Special tools and workshop equipment required
t  Depth gauge
t  Valve seat reworking tool
  Note
t  When repairing engines with leaking valves, it is not sufficient to replace valve seats and valves. It is also necessary to check the valve guides for wear. This particularly important on high mileage engines → Chapter.
t  The valve seats should only be reworked just enough to produce a perfect seating pattern. The maximum permissible reworking dimension must be calculated before reworking commences. If the reworking dimension is exceeded, the function of the hydraulic tappets can no longer be guaranteed and the cylinder head should be replaced.
Maximum permissible reworking dimension: calculation
–  Insert valve and press firmly against seat.
  Note
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 upper edge of cylinder head.
–  Calculate max. permissible reworking dimension from measured distance and minimum dimension.
Minimum dimensions:
   Inlet valve, 33.8 mm
   Exhaust valve, 34.1mm
Distance measured -a- minus the minimum measurement = maximum reworking dimension.
  V15-0640
Example:
 Distance measured35.1 mm
-Minimum dimension34.1 mm
=Max. permissible reworking dimension → Note1.0 mm

1)  The max. permissible reworking dimension is referred to in the diagrams as dimension “b”.
  Note
If the measured distance -a- is less than the minimum dimension, repeat the measurement procedure with new valves and if necessary use shorter valves (valve length -c- → Fig.) or replace the cylinder head.
   
Inlet valve seat: reworking
a - Ø 37.2 mm
b - max. permissible reworking dimension → Note
c - approx. 2.0 mm
Z - Cylinder head lower edge
45° - Valve seating angle
30° - Upper correction angle
  V15-0656
Exhaust valve seat: reworking
a - Ø 32.4 mm
b - max. permissible reworking dimension → Note
c - max. 2.4 mm
Z - Cylinder head lower edge
45° - Valve seating angle
30° - Upper correction angle
2)  Max. permissible reworking dimension → Chapter.
  Note
Those valve seats that come with a narrowing can only be reworked up to a point where the said narrowing is not damaged.
  V15-0657

Cylinder head: removing and fitting > < Crankshaft dimensions