DETROIT DIESEL 53
Exhaust Valves 1.2.2
brackets to the cylinder head and remove the brackets
The exhaust valve spring has a wire-diameter of 148"
and the shaft.
For service replacement, change the spring when a load
4. Remove the fuel injector.
of less than 25 lbs. will compress it to 1.93" (installed
length).
5. Place a block of wood under the cylinder head to
Inspect the valve spring seats and caps for wear.
If
springs as outlined in Steps 6 and 7 above.
worn, replace with new parts.
6. Turn the cylinder head over, using care to keep the
Carbon on the face of a valve indicates blow-by due to a
valves from falling out of the head. If the valves are to
faulty seat. Black carbon deposits extending from the
be reused, number each valve to facilitate reinstallation
valve seats to the valve guides may result from cold
in the same position. Then withdraw the valves from
operation due to light loads or the use of too light a
the cylinder head.
grade of fuel. Rusty brown valve heads with carbon
deposits forming narrow collars near the valve guides is
7. Remove the cam followers and push rod assemblies
evidence of high operating temperatures.
High
as outlined in Section 1.2.1 under Remove Cam
operating temperatures are normally due to overloads,
Follower and Push Rod Assembly (Cylinder Head
inadequate cooling, or improper timing which results in
Removed from Engine).
carbonization of the lubricating oil.
Inspection
Clean the carbon from the valve stems and wash the
valves with fuel oil. The valve stems must be free from
Clean the springs with fuel oil, dry them with
scratches or scuff marks and the valve faces must be
compressed air and inspect them. Replace a pitted or
free from ridges, cracks or pitting. If necessary, reface
fractured spring.
the valves or install new valves. If the valve heads are
warped, replace the valves.
Check the springs with spring tester J 9666 and an
accurate torque wrench. Replace a spring a load of less
Clean the inside diameter of the valve guides with or
than 25 pounds will compress a four valve cylinder head
brush J 7793 as shown in Fig. 4. This brush will remove
spring to 1.93 inches. The difference in the load
all gum and carbon deposits from the valve guides.
between a pair of
springs must not exceed 6
pounds or the valve bridge will be unbalanced.
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
.006" .005" replace the valve guides.
The valve guides, which are not machined for use with
oil seals, have a 45 chamfer at the upper end.
1972 General Motors Corp.
February, 1972
SEC. 1.2.2 Page 3
