Tappet Adjustment
VALVE
SYSTEM
The engine is equipped with adjustablevalve tappets.
The valve tappet clearance should be checked and
adjusted, if necessary, at least every
200
operating
hours or when poor engine performance is noticed.
Adjust the valve clearance only when engine is at
ambient temperature. Proceed as follows:
Aproperlyfunctioning valvesystem isessential forgood
engine performance. AI1 engines utilize an L-head type
valve design asshown in Figure
53.
Accessto thevalve
system can beobtained by removing the cylinder heads
and thevalvecoverson top
oftheengine.Avalvespring
'
comm-essor must be used to remove valves from the
1.
2.
3.
4.
5.
6.
7.
8.
Remove ignition key to prevent accidental star-
ting.
Remove all parts necessary to gain access to
valve tappets.
Remove spark plugs to ease the task of turning
the engine over by hand.
Place a socket wrench on the flywheel capscrew
and rotate the crankshaft in a clockwise direction
until
the left intake valve (viewed from flywheel
end) opens and closes. Continue turning the
crankshaft until the TC mark on the flywheel is
lined up with theTC mark on the gear cover. This
should place the left piston (#1) at the top of its
compression stroke. Verify that the left intake and
exhaust valves are closed and there is no pressure
on the valve lifters.
The correct feeler gauge for the valve adjustment
(SPECIFICATIONS)
should pass freely between
valve stem and tappet; a
0.002
inch
(0.05
mm)
thicker gauge should not (Figure
53).
To
correct the valve cleara'nce, use
a
7/16-inch
open end wrench to turn the adjusting screw to
obtain the correct clearance. The screw is self-
locking and will stay where
it
is set.
A
9/16-inch
(14 mm) open end wrench is required to hold the
tappet while turning the adjusting screw.
To adjust valves on the right hand cylinder, turn
engine one complete revolution and again line up
mark on the flywheel and theTC markon thegear
cover. Then follow adjustment procedure given
for left hand cylinder.
Replace all parts removed in Step
2.
Tighten all
screws securely. Torque manifold bolts
to
spec-
ified torque.
..
NOTE
cylinder block.
A valve stem seal
is
used on the intake valve guides of
some engines. This seal must be replaced each time the
valve
is
removed.
Placevalves, springs, retainers, and tappets in a rack as
they are removed from cylinder block
so
they can
be
identified and reinstalled in their original locations.
Discard old valve stem seals and replace with new ones
during assembly.
Use the following procedures to inspect and service the
valve system.
I
Inspection
Clean carbon from the valves, valve seats, valve
guides, and cylinder block.
Valves:
Check the valve face for evidence of burning,
warpage, out-of-round, and carbon deposits.
Burning and pitting are caused by the valve failing to
seat tightly. This condition is often caused by hard
carbon particles on the seat.
It
may also be due
to
weak valve springs, insufficient tappet clearance,
warpage, and misalignment.
VALVE
RETAINER>
\(
~~
VALVE
SPRING,
*:*w
'E
CI
XARANCE
USEASTANDARD
AU
WRENCH
TO
ADJUST
THE
TAI
VALVE
ADJUSTING
TOMOTIVE
TY
PE
VALVE
CLEARANCE
7
/
SCREW
N
'PETS.
H
.I
''
1
ONLY)
SEAL
I
VT-1005
FIGURE
53.
VALVE ASSEMBLY
40
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