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Engine lubrication > < Removing and installing cylinder head

Leon Mk1

Reworking valve seats
Reworking valve seats
Special tools and workshop equipment required
t  Depth gauge
t  Valve seat refacing tool
  Note!
t  When repairing engines with leaking valves, it is not sufficient to replace or renew 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 renewed.
The max. permissible reworking dimension is calculated as follows
–  Insert valve and press firmly against seat.
  Note!
If the valve is to be renewed 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 dimension: Inlet and exhaust valves 32.1 mm
Distance measured minus the minimum height = maximum check height admissible.
Example:
  V15-0640

-		Distance measured
Minimum dimension		32.5
32.1		mm
mm
=max. permitted rework dimension → Note0.4mm

1)  The max. permissible reworking dimension is shown on illustrations for reworking valve seats as dimension “b”
   
Reworking inlet valve seat
a - Ø 31.9 mm
b - max. permitted rework dimension → Note
c - 1.8 ... 2 mm max.
Z - Cylinder head lower edge
α - 45º valve seat angle
β - 30° upper correction angle
γ - 60° lower correction angle
2)  Calculating max. permissible reworking dimension → .
  N15-0146
Reworking exhaust valve seat
a -  Ø 26.6 mm
b - max. permitted rework dimension → Note
c - 1.8 ... 2 mm max.
Z - Cylinder head lower edge
α - 45° valve seat angle
β - 30° upper correction angle
γ - 60° lower correction angle
3)  Calculating max. permissible reworking dimension → .
  N15-0147

Engine lubrication > < Removing and installing cylinder head