Service Manual
Warpage occurs chiefly in the upper stem due to
its
exposure to intense heat. Out-of-round wear follows
when the seat is pounded by a valve whose head is not
in line with the stem and guide.
If
a valve face is burned
or warped, or
if
the stem is worn, install a new valve.
Too much clearance in the intake guide admits air and
oil into the combustion chamber, upsetting carburetion,
increasing oil consumption, and making heavy carbon
deposits. Carbon reduces heat dissipation. Clean metal
is a good heat conductor but carbon insulates and
retains heat This increases combustion chamber temper-
atures which causes warping and burning.
Unburned carbon residue gums valve stems and causes
them to stick in the guide. Deposits of hard carbon with
sharp points projecting become white hot and cause
pre-ignition and pinging.
Refinish valves that are slightly pitted
or
burned on an
accurate valve grinder.
If
valves are badly pitted or have
a thin margin when refacing, replace them.
FIGURE
2.
VALVE
STEM
AND
VALVE
GUIDE
INSPECTiON
Stems and Guides:
Always check valve stems and
guidesfor wear (Figure
2).
Use a hole gauge to measure
the valve guide. When clearance with stem exceeds that
specified in
DIMENSIONS AND CLEARANCES
replace
either valve or guide or both, as may
be
necessary.
Always regrind seat to make concentric with the newly
installed guide.
Worn valve stem guides can be replaced from inside the
valve chamber (a seal is provided behind the intake
valve guides only). The smaller diameter of the tapered
valve guides must face toward the valve head. Tappets
are also replaceable from the valve chamber after first
removing the valve assemblies.
Valve Guide Removal:
Before removing valve guides,
use an electric drill with a wire brush to remove carbon
and other foreign material from top surface of guides.
Failure to perform this operation may result in damage
to
the
guide bores. Drive the guides out with a hammer
and valve guide drive.
the
Drivlng
out
old
guides can damage
e
guide
or
tappet
bores.
Be
careful
not to strike guide
bores
with driver
or
allow
guide
to
strike
tappet
bores
during removal.
Valve Guide Installation
Run a small polishing rod
covered with crocus cloth through valve guide
holes
to
clean ,out carbon and other foreign materials. Place a
new gasket on the intake valve guide, and coat the outer
edge
of each new guide with oil. Place guide in cylinder
block and press in until guide protrudes
11
/32
inch
(8.7
mm) from valve
box
side of block.
A
suggested
method of installation is shown in Figure
3.
ROD
VALVE
GUIDE
5/16-18
HEX,
(2
REQUIRED)
\
THREADED ROD
W-1023
FIGURE
3.
VALVE
GUIDE
INSTALLATION
Valve Stem Seals (intake only):
Do
not reuse valve stem
seals. Each time the valves are removed from cylinder
block, a new
seal
must be used when valve is reinstalled.
not
remove valve after seal
is
installed. valve can
be
withdrawn
only as
far
as the groove in valve
stem.
Do
not
allow
valve stem
seal
to
come in contact with groove
or
seal
damage will
result.
10-3