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 TM 55-1905-220-14-4
3-33.2. EXHAUST VALVE - MAINTENANCE INSTRUCTIONS (Cont).
LOCATION
ITEM
ACTION
REMARKS
INSPECTION
12. Exhaust
Springs
Inspect.
Refer to step 3.
valve
springs
(4)
13. Exhaust
Bridge and
Inspect.
Refer to step 4.
valve
guide
bridge
(1) and
guide (6)
14. Exhaust
Carbon on the face of a valve indi-
valves
cates blow-by due to a faulty seat.
(10)
Black carbon deposits extending from
the valve guides may result from
cold operation due to light loads or
the use of too light a grade of fuel.
Rusty brown valve heads with carbon
deposits forming narrow collars near
the valve guides evidence hot opera-
tion due to overloads, inadequate
cooling, or improper timing which
results in carbonization of the
lubricating oil.
Clean the carbon from the valve
stems and wash the valves with fuel
oil. The valve stems must be free
from scratches or scruff marks and
the valve faces must be free from
ridges, cracks, or pitting. If
necessary, reface the valves or
install new valves. If the valve
heads are warped, replace the
valves.
If there is evidence of engine oil
running down the exhaust valve stem
into the exhaust chamber, creating a
high oil consumption condition
because of excessive idling and
resultant low engine exhaust back
pressures, install valve guide oil
seals.
3-722
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