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Camshaft oilseals renew > < Servicing valve gear repairing

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Valve seats reworking
Valve seats reworking
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 is 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.
Calculate the max. permissible reworking dimension
–  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 dimensions:
   Inlet valve 7.6 mm
   Exhaust valve 7.6 mm
Distance measured minus minimum dimension = maximum acceptable reworking dimension.
Example:
  N15-0079
Measured distance8,0 mm
- Minimum dimension7,6 mm
= max. perm. rework dimension → Note0,4 mm

1)  The max. permissible reworking dimension is shown on illustrations for reworking valve seats as dimension “b”.
   
Reworking inlet valve seat reworking
a - Ø 28,7 mm
b - max. perm. rework dimension → Note
c - 1,5...1,8 mm
Z - valve lower edge
α - 45° valve seat angle
β - 30° upper correction angle
g - 60° lower correction angle
Reworking exhaust valve seat: reworking
a - Ø 25,0 mm
b - max. perm. rework dimension → Note
c - approx. 1.8 mm
Z - valve lower edge
α - 45° valve seat angle
β - 30° upper correction angle
g - 60° lower correction angle
2)  Calculating max. permissible reworking dimension → .
  N15-0096

Camshaft oilseals renew > < Servicing valve gear repairing