TM 5-4320-21 8-15
Section VIII. CYLINDER HEADS AND VALVES
on the cap screws and tighten to 25-
32 foot-pounds torque in the sequence
Each of the two L-type cylinder heads is se-
c u r e d to the cylinder blocks with 17 cap
screws and plain washers. They must be re-
moved if it is necessary to regrind the valves
a. General. The valves are lifted by mush-
or to do work on the pistons and connecting
rods. The valves are roto type valves, and
The tappets are raised by the lobes of the cam-
can be adjusted by removing the valve cover
shaft, and cannot be replaced without remov-
ing the camshaft. The firing order of the cyl-
inders is 13--42. Number 1 cylinder is the
nearest one to the flywheel in the left bank of
cylinders; number 3 cylinder is the other one
(1) Remove the cylinder head shrouds
in this bank. Number 2 cylinder is the nearest
a n d rear shroud covers (par. 72).
one to the flywheel in the right bank of cylin-
(2) Remove the manifold.
ders and number 4 is the other.
(3) Remove the spark plugs.
b. Tappet clearance adjustment.
(4) Remove the 17 capscrews (13 and
(1) Make sure engine is cold. Remove
16, fig. 30) and washers (12) that se-
cure each cylinder head (11) to the
ers (2) that secure the valve covers
cylinder blocks (7); remove the cyl-
(3) to the cylinder blocks (7); re-
inder heads and gaskets (10).
move the valve covers and gaskets
b. Cleaning and inspection.
(1) Carefully scrape and wire brush all
(2) Remove the flywheel screen.
carbon deposists from the cylinder
(3) Remove the spark plug from the No.
blocks. Clean the carbon from the
tops of the pistons and blow away the
(4) Crank the engine slowly until the pis-
carbon with compressed air.
ton rising in the compression stroke
(2) Wire brush and scrape the carbon
blows air out of the spark plug hole.
out of the cylinder heads.
Continue cranking until the marked
(3) Wipe the cylinder heads and blocks
vane on the flywheel alines with the
with a cloth dampened with an ap-
No. 1 centerline mark on on the fly-
wheel shroud which is 45 degrees
counterclockwise from the vertical as
(4) Inspect the cylinder heads for cracks,
breaks, or warping; replace a defec-
(5) Adjust the exhaust valve tappet clear-
tive cylinder head.
ance to .016 inch. Adjust the inlet
(5) Inspect the top of the cylinder block
valve tappet clearance to .008 inch.
for cracks or breaks. Inspect the cyl-
(6) Turn the engine crankshaft 180 de-
inder walls for scoring and pitting.
grees clockwise, a n d adjust tappet
(6) I n s p e c t the top of the valves and
clearance on the No. 3 cylinder.
valve seats. Repair or replace any de-
fective valves (see appropriate sec-
tion in this manual for detailed in-
(1) Install the cylinder heads in the re-
verse manner outlined in a above.
(7) Turn the crankshaft clockwise until
(2) Apply a mixture of graphite and oil
the marked vane is alined with the