Jeep UNIVERSAL CJ-2A - Page 87

E
F4-l34 ENGINE
c. When pressure is higher than normal it indicates
that carbon deposits in the combustion chamber
have reduced the size of the chamber enough to
give the effect of a raised compression ratio. This
will usually cause pinging under load that cannot
be satisfactorily corrected by timing. The carbon
must be cleaned out of the engine to correct this
trouble.
d. Reinstall the spark plugs. Torque with a wrench
to proper setting.
E-107. VALVE ADJUSTMENT
Proper valve adjustment is important to prevent
burning of valves and poor engine performance.
This adjustment consists of obtaining a specified
lash
in the valve mechanism. The exhaust valve
tappets and the intake valve rocker arms should
be adjusted to the proper clearance with the engine
cold
(at room temperature). Valve clearance can
be properly adjusted only when the tappet is on the
heel qr low portion of the cam.
E-108. Valve Adjustment Procedure
The exhaust valve tappets are adjusted byturning
the adjusting screw in or out of the tappet as neces-
sary to obtain the proper clearance. Where special
wrenches
can be obtained, they should be used to
facilitate the adjustment. The proper clearance is
.016" [0,406 mm.] between the end of the adjusting
screw and the bottom of the exhaust valve.
Crank the engine over to close a. valve and check
the clearance with a feeler gauge. To adjust, hold
the tappet with one wrench and turn the adjusting
screw, with the other. Check and adjust each of
the. tappets in proper sequence.
Adjust each intake valve by adjusting the rocker
arm screw at the push rod to obtain .018" [0,457
mm.] clearance between the rocker arm and the
valve stem with tappet on the heel of the cam.
E .. 108A. Vacuum Check
Disconnect the vacuum line fitting from the head
just below the carburetor and install the proper
adapter. Connect a vacuum gauge to.the adapter
and start the engine. Connect a tacho,meter from
the distributor primary terminal to ground and set
the engine speed at the correct rpm. (F4-134 engine:
600 rpm.). Observe the vacuum reading and in-
terpret as follows:
a. A steady reading from 18 to 21 inches [46 a 63
em.]
o( mercury [Hg] is a normal reading indicat-
ing that valve and spark timing, valve seating,
and piston ring sealing are all satisfactory.
b. A steady but below normal reading indicates a
condition common to all cylinders such as a leak
at the carburetor gasket, late, ignition or valve
timing, or uniform piston-ring-and-bore wear.
e. A slowly fluctuatine; or drifting reading indicates
that the idle mixture is incorrect and the cause
should be looked for in the fuel system.
d. A rhythmic pulsating reading is caused by a
condition affecting one or more cylinders, but not
all, and indicates leaky valve, gasket blowby, re-
stricted intake port, or an electrical miss.
e. An intermittent pulsating reading is caused by
an occasional malfunction such as a sticking valve
(all valves may' be erratic in operation if the valve
86
springs
are· weak), or electrical miss .caused by
insufficient distributor point tension or low coil
voltage coupled with inconsistent spar_k 'plug gaps
or fouled plugs, or dirt in the fuel system finding
its way into passages of critical size or valve seats
in the carburetor.
f. A normal reading that quickly falls off (with
engine running at 2000 rpm.) indicates exhaust
back-pressure caused by a restriction in the exhaust
system.
E-109. Check Valve Timing
To check the valve timing, carefully set the intake
valve rocker arm adjustment for No. 1 cylinder to
.026" [0,6604 mm.] between the rocker arm and the
valve stem. Rotate the crankshaft clockwise until
the piston in No. 1 cylinder is ready for the intake
stroke. The intake valve opens go before top center
(BTC). Note the distance between the "TC" and
"5°" marks on the indicator on the tin1ing gear
cover and estimate the go before top center position.
See Fig. 110. With the crankshaft in this position,
timing is correct if the rc;>cker arm is just tight:
against the intake valve stem. Do not overlook
resetting the rocker arm adjustment to the correct
running clearance.
50° ABC 47° BBC
10270
FIG. 110-VALVE TIMING·
E-110. OILING SYSTEM
The engine oil pressure system is designed to pro-
vide adequate lubrication to all working parts of
the engine. The gear-type oil pump is driven from
the engine camshaft. The pump is provided with a
floating,
screened intake that prevents the circula-
tion of any !!ediment that might accumulate in the
oil pan. By means of this pump, the main bearing
journals and crankpins are efficiently lubricated
through an oil gallery and passages in the cylinder
block. Oil is forced under pressure to the main
bearings and through the cheeks of the crankshaft
to the connecting rod. bearings. Oil is also force-fed
to the camshaft bearings, timing gears, and inta~e
valve rocker arms. The oil pressure is controlled by
relief valve located in the oil pump. The valve is