Tappet Adjustment
VALVE
SYSTEM
The engine is equipped with adjustable valve 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:
A
properly functioning valve system isessential for good
engine performance.
All
engines utilize an L-head type
valve design as shown in Figure
1.
Access
to
the valve
system can be obtained by removing the cylinder heads
and thevalve coverson top of the engine. Avalvespring
compressor must be used to remove valves from the
t
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 the TC 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
(see SPEClFlCATl0NS)shouId pass freely between
valve stem and tappet; a
0.002
inch
(0.05
mm)
thicker gauge should not (Figure 1).
To correct the valve clearance, 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 the TC mark on the gear
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:
USEA STANDARD AUTOMOTIV
WRENCH TO ADJUST THE TAI
J
cy1
i
nder 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.
Place valves, 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 valvestem seals and replace with new ones
during assembly.
Use the following procedures to inspect and service the
valve system.
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 ADJUnlNG
SCREW
'ETYPE VALVE CLEARANCE
'PETS.
pj
VALVESPRING,
E
VALVE RETAINER
CTT
,
VALVE
SEAT
''
I
ONLY) SEAL
I
ALVE ROTATOR
I
FIGURE
1.
VALVE
ASSEMBLY
I
VT-1005
10-2
Redistribution or publication of this document,
by any means, is strictly prohibited.
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