14-78. Cleaning, Inspection and Repair.
Cleani ng and Inspection of Cylinder Head.
(1) Steam-clean cylinder head.
(2) Clean deposits of salt, lime or sludge
(3) Submerge cylinder head in tank of cleaning
solution, Federal Specification P-D-680 heated to
near boiling point.
Remove and dry thoroughly.
(4) Clean crossheads, valves, and valve
springs by submerging in solvent. Remove from
solvent tank and dry thoroughly.
(5) Clean valves with buffer and polish with
(6) Examine cylinder head carefully for cracks.
b. Valve Spring, Valve Guide, Valve Seat and
Valve Inspection and Repair.
(1) Inspect valve springs for cracks. Place
spring in test stand.
Both intake and exhaust valve
springs with dampers should have a load of 40-46
pounds when compressed to a length of 2.237 inches
(valve closed) and a load of 105-115 pounds when
compressed to a length of 1.780 inches (valve open).
Install new spring when old spring is 5 percent under
or over load limits.
(2) Replace intake and exhaust valves if they are
cracked, bent, burned or stems are worn. The outer
diameter of exhaust valve stem is 0.3705 to 0.371
inch. Bore of exhaust valve guide is 0.3725 inch
giving stem-to-guide clearance of 0.0015 to 0.002
inch. Replace exhaust valve and/or guide if clearance
exceeds 0.0055 inch. Outer diameter of intake valve
stem is 0.3715 to 0.372 inch. Bore of intake valve
guide is 0.3725 inch giving stem-to-guide clearance
of 0.0005 to 0.001 inch. Replace intake valve and/or
guide if clearance exceeds 0.0035 inch.
(3) Inspect valve seats. Replace
pitted, or loose.
Removal is described
in para 14-77.
(1) Inspect valve seat counterbores for clean-
liness, burrs, and correct size. (1. 655 to 1.666
inches for exhaust valve, 1.809 to 1.810 inches for
intake valve, 1.670 to 1.671 inches for 0. 005 inch
oversize exhaust valve end 1.814 to 1.815 inches for
0.005 inch oversize intake valve).
(2) Depth of exhaust valve bore is 0.4735 to
0. 4755 inch and 0. 4585 to 0. 4605 inch for intake valve.
(3) Chill inserts for two to four minutes in a
dry ice container or cold box.
(4) Place cylinder head bottom side up on a
bench. Thoroughly clean counterbores for the inserts
with compressed air and start an insert into the count-
terbore (valve seat side up).
(5) Use a valve seat insert installing tool and
drive insert down tightly into counterbore. This
operation must be done quickly while insert is cold.
(6) Exhaust valve seat inserts must be staked
to eliminate the possibility of the insert loosening in
d. Valve Face and Valve Seat Grinding.
Before installing either new valves or used
valves, valve seats in cylinder head should
be inspected for proper valve seating. If
used valves are to be reinstalled, valve
stems should be cleaned and valve faces
ground to angles of 30° for exhaust and in-
take valves. When refacing valves, remove
all evidence of pitting and grooving. The
valve guide should be cleaned with a nylon
brush. If bore in valve guide is worn oblong,
or if valve head is warped relative to valve
stem, the necessary parts must be replaced.
When new valve seat inserts are installed,
or used inserts reseated, refinishing must
be done with a valve seat grinder.
(1) The cutting face of the stone must be main-
tained at the correct angle and in proper condition by
frequent dressing with a diamond wheel dresser. The
frequency of dressing will be determined by condition
of the seats and amount of metal required to be re-
moved during the grinding operation.
c. Valve Seat Insert Installation.
Press fit of valve seat inserts must be
If insert bores in cylinder
head are badly worn, bores must be
machined 0.005 inch larger than original
bore. Valve seat inserts 0.005 inch
oversize must be installed.
By grinding valve face and insert seat at
slightly different angles, a fine line con-
tact of the face and seat is obtained, thus
eliminating the need to lap the seating sur-
faces with grinding compound.
(2) The difference of angles is usually 1/2 to
1-1/2°. The angle of the insert seat is made greater
than that of the valve face, so as to assure contact
14-78 Change 3