NOTE
Do not bend the fuel pipes and do
not exceed the specified torque.
Excessive tightening will twist or
fracture the flared end of the fuel
pipes and result in leaks. Lubri-
cating oil diluted by fuel oil can
c a u s e serious damage to the engine
8. Fill the cooling system.
9. Adjust the exhaust valve clearance
a n d time the injectors.
10. If necessary, perform an engine tune
up.
Figure 11B-49. Location of Exhaust
EXHAUST VALVES
Valves
E x h a u s t Valve Maintenance
Description
Efficient combustion in the engine re-
quires that the exhaust valves be main-
Four exhaust valves are provide for each
tained in good operating condition.
cylinder (see Figure 11B-49). The valve
Valve seats must be true and unpitted to
heads are heat treated and ground to the
assure l e a k p r o o f s e a t i n g , v a l v e s t e m s
proper seat angle and diameter. The
must work freely and smoothly within the
valve stems are ground to size and hard-
ened at the end which contacts the ex-
valve guides and the correct valve clear-
haust valve bridge.
ance must be maintained.
The exhaust valve stems are contained
Proper maintenance and operation of the
engine is important to long valve life.
within exhaust valve guides which are
Engine operating temperatures should be
pressed into the cylinder head.
m a i n t a i n e d between 160-185F (71-85C).
Low operating temperatures (usually due
Exhaust
valve
seat
inserts
to extended periods of idling or light en-
(Figure
11B-50
on
page
11B-341,
gine
loads)
result
in
incomplete
pressed into the cylinder head permit
combustion, formation of excessive car-
accurate seating of the exhaust valve
bon deposits and fuel lacquers on valves
under varying conditions of temperature
and related parts, and a greater tenden-
and materially prolong the life of the cyl-
inder head. The exhaust valves are
cy for lubricating oil to sludge.
ground to a 30 seating angle while the
exhaust valve seat inserts are ground to
Unsuitable fuels may also cause formation
a 31 seating angle.
of deposits on the valves, especially
when operating at low temperatures.
The exhaust valve springs are held in
When carbon deposits, due to partially
place by the valve spring caps and ta-
burned fuel, build up around the valve
pered two-piece valve locks.
stems and extend to that portion of the
stem which operates in the valve guide,
Excess oil from the rocker arms lubricate
sticking valves will result. Thus, the
the exhaust valve stems. The valves are
valves cannot seat properly and pitted
cooled by the flow of air from the blower
and burned valve and valve seats and
past the valves each time the air inlet
loss of compression will result.
ports are uncovered.
Lubricating oil and oil filter should be
c h a n g e d periodically to avoid the accumu-
lation of sludge.
Engine (Less Major Assemblies)