Inspection
Valve Face:
Check the valve face for evidence of burn-
ing, warping, out-of-round, and carbon
deposits
(see
Figure
9-6).
Burning and pitting are caused by the valve failing to
seat tightly. This condition is often caused by hard car-
bon particles on the seat.
It
may also be due
to
weak
valve springs, insufficient tappet clearance, warping,
Warping occurs mainly due to 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 the stem
worn, install a new one.
Too
much clearance in the intake guide admits air and
oil into the combustion chamber, affecting carburetion,
increasing oil consumption, and making heavy carbon
deposits. Clean metal is a good heat conductor but
carbon insulates and retains the heat. This increases
combustion chamber temperature which causes warp-
ing and burning.
.
and misalignment.
VALVE
SPRINGS
VT-1037
FIGURE
9-4.
OVERHEAD VALVE
SYSTEM
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.
Valve Removal
The valves can be removed from the cylinder head
without the use
of
special tools. Depress the valve
spring retainerusing a9/16inch crowsfootona6inch
extension and remove keeper. See Figure 9-5. Remove
spring retainer and spring, then remove valve.
FIGURE
9-5.
VALVE REMOVAL
VALVE FACE
VALVE
GUIDE
VALVE STEM
VT-1038
VT-1020-1
FIGURE
9-6.
VALVE FACE, VALVE STEM AND VALVE GUIDE
INSPECTION
9-3
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