guides, and 2 7/8 inches for the
(5)
Remove the intake and exhaust
exhaust valve guides.
manifold (TM 5-5820-205-20/2).
(3)
Valve seat inserts are used only for
(6)
Remove the water pump (par. 45).
the exhaust valves, and are held in
Note. If only the rear cylinder head
place by a shrink fit. Inspect all
assembly is being removed it is not
exhaust valve inserts in the cylinder
necessary to remove the water pump.
head and replace any that are loose,
cracked, or otherwise damaged. It is
(7)
Remove the rocker arm assemblies
not recommended to install a new
insert having the same outside
(8)
Refer to figure 20 and remove the
diameter as the one removed. When
cylinder head assembly from the
replacing an oversize insert, clean
engine.
and remachine the counterbore for a
Disassembly.
Refer to figure 22 and
b.
0.010 in. larger insert than the one
disassemble the cylinder head assembly.
removed. Use a tool with a correct
fitting pilot.
When machining the
78.
Cylinder Head Assembly Cleaning, Inspection,
counterbore, be sure to go deep
and Repair
enough with the tool to clean the
a.
Cleaning.
bottom so that the insert will have full
contact to carry away the heat. The
(1)
Clean all parts in an approved
outside diameter of the inserts is
cleaning solvent.
Be sure all oil
2.2545 in. to 2.2535 inches. The
galleries are open and clean.
inside diameter of the counterbore is
(2)
Clean all valve stem guides,
2.251 in. to 2.250 in. and a press fit
removing lacquers or other deposits
would be 0.0067 in. to 0.0052 inch.
by running a valve guide cleaner or
(4)
The new insert, when installed, should
wire brush through the reamed hole.
have a press fit. Chill the insert in a
(3)
Clean the inside chambers and
container of dry ice for 20 minutes
passages of the energy cell using
before installing.
scraper and drill.
(5)
Inspect valves for condition and
b.
Inspection and Repair.
replace any that are nicked, cracked,
(1)
Inspect the guides for wear by using a
burned, and those on which the valve
telescopic gage and a one-inch
stems are bent or worn more than
micrometer. Replace all guides that
0.002 inch. Replace or reface all
are worn more than 0.0015 inch in
defective valves.
diameter. The maximum length for
(6)
Install the pilot in the valve stem
the intake valve stem guides is 4.718
guide. Set the stone to an angle of 45
in., the maximum length for the
degrees on the valve reseating outfit.
exhaust valve stem guides is 3.812
Place the grinder and stone assembly
inch. The valve guide stem hole
over the pilot on the valve guide and
diameter for the intake valve is from
grind just enough to remove all pits
0.4985 to 0.4990 in. and for the
and grooves end to have a new cut
exhaust valve it is from 0.498 to
show evenly all around the seat.
0.4996 in. The outside diameter for
Check the seat for concentricity with a
both the intake and exhaust valve
dial indicator.
guides is from 0.8755 to 0.8765 inch.
(7)
Install the valves in a suitable grinder
(2)
The old valve guides are pressed out
making sure that the grinding wheel is
of the cylinder head by pressing from
properly true and that the chuck is set
the combustion chamber side. The
at the proper angle. Care should be
new valve guides are pressed in from
taken while grinding not to remove too
the combustion chamber side to a
much material from the face. After
depth below the cylinder head surface
of, 2 inches for the intake valve
AGO 3456A
54