Minor Engine Service Operations; Cylinder Head Gasket; Valve Clearance Adjustment; Adjusting The Clearance - International Harvester Company CUB Operator's Manual

CYLINDER HEAD GASKET
Adjusting the Clearance
Check the tightness of the cylinder head
bolts after the first 50 hours of engine opera-
tion for a new tractor and 50 hours after in-
stalling a new cylinder head gasket. The bolts
should be tightened to from 45 to 50 foot-
pounds torque.
1. To safeguard against accidentally starting
the engine when checking the valve clearance,
remove cable liB" from the coil cover on the
magneto (Illusts. 29 and 29A) or remove distributor-
to-coil cable I'A'I from the socket on the coil of
the battery ignition unit. See "lust. 31A.
z. Remove the valve cover from the left side
of the crankcase.
For most satisfactory results in tightening
the cylinder head after installing the cylinder
head gasket, tighten down all the cylinder head
bolts fairly snug, starting with the row in the
center, then going to the others. Retighten in
the same order, giving each bolt a fraction of
a turn at a time. Continue this until all bolts
are tight. Do not screw one bolt down perfectly
tight and then go on to the next as you will not
obtain an even pressure on the gasket in this
manner.
3. Remove the spark plug from the No. 1
cylinder (the cylinder next to the radiator).
4. Place your thwnb over the spark plug
opening and slowly crank the engine until an
outward pressure is felt. (Pressure indicates
that the No. 1 piston is moving toward the top
dead center of the compression stroke. ) Con-
tinue cranking slowly until the top dead center
mark (second notch on the back flange of the
fan drive pulley at the left side of the engine)
is in line with the timing pointer in the front
crankcase cover. See !llust. 32. Both valves are
now closed on the compression stroke of theNo.
1 cylinder.
After replacing the cylinder head, it isnecessary
to insure against leaks by retighten.
ing the bolts after the engine has been operat-
ing and the water jacket has become thoroughlyheated.
5. Use two thin wrenches when adjusting the
valve clearance. See Illust. 42. Use the lower
wrench to hold the tappet and the upper wrench
to raise or lower the tappet adjusting screw. A
gauge of .Ol5-inch thickness should slip snugly
between the valve stem and the tappet adjusting
screw.
CRANKSHAFT BEARINGS, PISTONS, AND RINGS
We cannot impress too strongly the neces-
sity of having your International Harvester
dealer do the work of replacing the connecting-
rod bearings, crankshaft bearings, pistons
and rings, and reconditioning the valves.
6. Starting at the front of the engine, adjust
valves No. 1,2,3, and 5. Then crank the
engine one complete revolution and adjust
valves No.4, 6, 7, and 8.
VALVE CLEARANCE ADJUSTMENT
Check the valve clearance after every 500
hours of operation and adjust the clearance if
necessary. A clearance of .015 inch, measured
when the valves are closed and the engine is
cold, is necessary between the end of the tap-
pet adjusting screw and the valve stems.
When engine valves are equipped with pos-
itive-action valve rotators, check the valve
clearance after 50 hours of operation, and
after every 150 hours thereafter until the
clearance remains the same between two
checks.
All valves can be adjusted accurately by
cranking the engine only twice. Four valves
are adjusted when the No. I piston is at TDC
(compression) and the 'remaining four valves
are adjusted when the No.4 piston is at TDC
(compression).
Illust.42
Adjusting and checking valve clearance.
42