33
Cylinder head
Valve seat, replacement
(12A-14)
1
Install a new valve guide, operation 12A-11.
2
Work a small segment from the inside of one side of
the valve seat to a depth of 8.25 mm from the sur-
face of the cylinder head. Split the seat at the thin-
nest point and remove it from the cylinder block.
Clean the seat position and check that there are no
cracks.
3
The valve seat must be installed with the cylinder
head hot and the seat cold. Heat the whole cylinder
head slowly and evenly to approximately 100°C and
if possible cool the seat with liquid nitrogen to –
35°C. If liquid nitrogen is not accessible, cool the
seat down as much as possible in a freezer. Install
the seat with exterior bevel turned to the inside of
the head. Ensure that the bottom of the seat has
good contact with the bottom of the position in the
cylinder head.
WARNING! Use suitable gloves as protection
against the hot metal and the cold seat.
4
Mill the valve seat, 12A-13 and carefully lap the
valve and valve seat. Ensure that the valve crown
depth under the cylinder head surface is within the
production parameters, see Workshop Manual
“Technical Data”. Work as closely to the minimum
value to allow for later valve seat wear.
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