using a slight pressure, one-half turn to the right
and then one-half turn to the left. If rotating
removes the pencil marks, the seating is good.
Another method for checking the valve seating
is to coat the valve face lightly with Prussian blue
and turn it about one-fourth turn in the seat. If
the Prussian blue transfers evenly to the valve seat,
it is concentric with the valve guide. Be sure to
wash all the Prussian blue from the seat and valve.
Then lightly coat the valve seat with Prussian blue.
If the blue again transfers evenly, this time to
the valve when it is turned in the seat, you can
consider the seating to be normal.
VALVE SEAT INSERT
Some engines are equipped with valve seat
inserts that may be replaced when they are badly
worn or burned or have been ground down to the
point where there is not enough metal to permit
another grind. You can remove the old valve seat
by using a special puller, such as the one shown
in figure 3-23. However, if a puller is not
available, you can punch mark each side of the
insert and then drill almost through. After
drilling, take a hammer and chisel and break the
insert into halves for easy removal.
Before installing a new insert, chill it for 15
minutes in dry ice or by any other chilling method.
Chilling shrinks the insert so that it will fit in
place. You may then drive it in place and grind
VALVE SPRING TESTING
Valve springs should be tested for uniform
height and proper tension. To test for uniformity
Figure 3-23.Puller used in removing valve seat inserts.