DETROIT DIESEL 53
Exhaust Valves
1.2.2
brackets to the cylinder head and remove the brackets
and the shaft.
4. Remove the fuel injector.
5. Place a block of wood under the cylinder head to
support the exhaust valves. Remove the exhaust valve
springs as outlined in Steps 6 and 7 above.
6. Turn the cylinder head over, using care to keep the
valves from falling out of the head. If the valves are to
be reused, number each valve to facilitate re-
installation in the same position. Then withdraw the
valves from the cylinder head.
7. Remove the cam followers and push rod assemblies
as outlined in Section 1.2.1 under Remove Cam
Inspect the valve spring seats and caps for wear. If
Follower and Push Rod Assembly (Cylinder Head
worn, replace with new parts.
Removed from Engine).
Carbon on the face of a valve indicates blow-by due to
a faulty seat. Black carbon deposits extending from the
valve seats to the valve guides may result from cold
Inspection
operation due to light loads or the use of too light a
grade of fuel. Rusty brown valve heads with carbon
Clean the springs with fuel oil, dry them with
deposits forming narrow collars near the valve guides
compressed air and inspect them. Replace a pitted or
is evidence of high operating temperatures. High
fractured spring.
operating temperatures are normally due to overloads,
inadequate cooling, or improper timing which results
Check the springs with spring tester J 9666 and an
in carbonization of the lubricating oil.
accurate torque wrench. Replace a spring if a load of
less than 33 pounds will compress a two valve cylinder
Clean the carbon from the valve stems and wash the
head spring to 2.31 inches, or a load of less than 25
valves with fuel oil. The valve stems must be free from
pounds will compress a four valve cylinder head spring
scratches or scuff marks and the valve faces must be
to 1.93 inches. The difference in the load between a
free from ridges, cracks or pitting. If necessary. reface
pair of four valve cylinder head springs must not
the valves or install new valves. If the valve heads are
exceed 6 pounds or the valve bridge will be
warped, replace the valves.
unbalanced.
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 pressure,
replace the valve guide oil seals or, if not previously
used, install valve guide oil seals.
Clean the inside diameter of the valve guides with
brush J 7793 (four
valve head) as shown in Fig. 4. This brush will remove
all gum and carbon deposits from the valve guides.
Inspect the valve guides for fractures, scoring or
excessive wear. Check the valve-to-guide clearance,
since worn valve guides may eventually result in
improper valve seat contact. If the clearance exceeds
.005 " (four valve head),
replace the valve guides.
The current valve guides, which are not machined for
use with oil seals, have a 45 o chamfer at the upper
end. They replace the former 15 o chamfer valve
guides for service.
SEC. 1.2.2 Page 3
August, 1972
