INSPECTION OF THE VALVES,GUIDES AND SPRINGS (Contd)
Heavy carbon or varnish deposits on the
valve, Figure M-10, should be removed be-
fore valves are ground. This condition is
usually caused by worn piston rings and
bore which allow too much oil to reach the
combustion chamber. This condition could
also
be caused by worn valve guides. These
conditions should be corrected or the same
trouble with the valves will happen again.
Figure M-10
Inspect the valve head
for dishing and the
valve face for deep burned spots, Figure
M-11. These conditions can't be corrected
by grinding the valves. The valves should be
replaced. These conditions are usually cau-
sed by running the engine under excessive
load, at high engine temperatures.
~RNED
~~CE
Figure M-11
Valves with worn lock grooves or the
stem is worn or dished beyond the chamfer
must be replaced, Figure M-12.
WORN RETAINER GROOVE
WORN STEM TIP
Figure M-12
The checking of
the valve stem diameter
can best be done with
a good accurate mi-
crometer Figure M-13,
Figure M-13
The valve stem should not vary more
than the wear limits given in the "Specifica-
tion" Section
at any point on the valve stem,
If this condition exists, the valves must be
replaced.
The checking of the valve face :runout
should be done after the valves have been
ground.
A Vee block type holder with a dial
indicator, Figure M-14, should be used to
check the valve face runout, The valve face
should not vary more than the specification
given in the "Specification" Section, The
valve stem runout can also be checked with
this Vee block and dial indicator.
CHECKING VALVE
FACE RUNOUT
Figure M-14
IIINJRTAIIT
Small amounts ofveryfinepitting, Figure
M-15, may be found on the surfaces
of the
valve faces and seats after the valves are
cleaned.
Figure M-15
These are normal and will not
affect en-
gine performance, This fine pitting is caused
by a normal oxidation process and can hap-
pen on any engine during the run-in-period,
It is not necessary to grind valves or seats
if this fine pitting is found as the pitting will
generally :reoccur after the engine is run for
a few hours.
M-7
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