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 Follower and
Push Rod Assembly (Cylinder Head Removed from Engine).
Inspection
Clean the springs with fuel oil, dry them with compressed air and inspect them. Replace a pitted or fractured spring.
Check the springs with spring tester J 9666 and an accurate torque wrench. Replace a spring if a load of less than 33
pounds will compress a two valve cylinder head spring to 2.31 inches, or a load of less than 25 pounds will compress a
four valve cylinder head spring to 1.93 inches. The difference in the load between a pair of four valve cylinder head
springs must not exceed 6 pounds or the valve bridge will be unbalanced.
Inspect the valve spring seats and caps for wear. If worn, replace with new parts.
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 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 is evidence of high operating
temperatures. High operating temperatures are normally 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 scuff 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 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 chamfer at the upper end. They
replace the former 15 chamfer valve guides for service.
August, 1972
SEC. 1.2.2
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