in the chuck. If the valve is centered properly, then
the valve stem is bent and the valve must be
replaced. Remove only the amount of metal
necessary to true up t he face and remove the pits.
Make sure there is a proper margin of thickness,
as shown in figure 3-17. If this margin cannot be
retained after refacing, the valve must be
There are many different makes and models
of valve-refacing machines. Make sure that you
read and understand the instructions that apply
to the machine you are using.
VALVE GUIDE SERVICING
When servicing valve guides, remember that
the guides must be clean and in good condition
for normal valve seating. If, after cleaning a valve
guide, you find it worn, remove it and install a
new one. To remove old or worn valve guides and
install new ones, you need special guide removing
and replacing tools.
One procedure for checking valve guide wear
is as follows. Remove the cylinder head from the
vehicle to a clean safe working area. Remove the
valve springs and clean the valves and valve
guides. Insert the valve into the guide, allowing
the valve to remain off of its seat. Attach a dial
indicator to the cylinder head with the gauge
button just touching the edge of the valve head.
Watch the dial indicator gauge face, and move
the valve head sideways to determine the amount
of valve guide wear.
Another checking procedure involves the use
of a small hole gauge to measure the inside
diameter of the guide and a micrometer to
measure the valve stem; the difference in the
readings will be the clearance. When the
maximum clearance is exceeded, the valve guide
needs further servicing before you can proceed.
If the valve guide is of the integral type, you must
Figure 3-17.Proper valve margin of thickness after
ream it to a larger size and install a valve with
an oversized stem. But if the guide is replaceable,
you should remove it and install another one.
To remove valve guides, you will need a special
puller. On many L-head engines, you can drive
the guides down into the valve spring compart-
ment and then remove them. You can use an
arbor press to remove guides from the overhead
type of engines.
To replace the guides, use a valve guide driver
or a valve guide replacer except on overhead valve
engines, where an arbor press is necessary. In any
case, the guides must be installed to the proper
depth in either the block or head, as specified by
After the valve guides are serviced and the
valve seats ground, check the concentricity of the
two with a dial indicator. (See fig. 3-18.) Any
irregularity in the seat will register on the dial.
VALVE SEAT GRINDING
Two general types of valve seat grinders are
in use. One is a concentric grinder; the other, an
eccentric grinder. Only the concentric grinder is
discussed here because of its greater availability.
In the concentric valve seat grinder (fig. 3-19),
a grinding stone of the proper shape and angle
Figure 3-18.Determining concentricity of the valve seat
with a dial indicator.