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Page Title:
Engine Assembly Ignition Timing |
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 begin to open at a slight clockwise
(1) If the engine is normal, a vacuum of
movement of the cam.
approximately 18-inch suction pres-
sure will be indicated. "The pressure
(5) To adjust distributor, loosen nut hold-
will drop to about 3 inches when the
ing clamp then rotate distributor
throttle is opened and will increase to
counterclockwise to advance the tim-
about 22 inches when the throttle is
ing, or clockwise to retard the timing.
closed.
Tighten nut to lock distributor in this
position. Install seal plate and rotor.
(2) A vacuum of 15 or 16 inches, with a
steady needle, indicates that the piston
(6) If a test lamp is available, connect one
rings, pistons, or lubricant are prob-
lead to the terminal post and the other
ably in PC-r condition. Slight needle
lead to a ground on the distributor.
motion indicates late ignition timing.
With ignition switch ON, the lamp
will light when points are closed and
(3) A vacuum of 8 to 12 inches with a
will go OUT as soon as points open.
steady needle indicates worn valve
guides, worn piston rings, poor lub-
b. Neon Light Method. The neon light, when
ricant, or an intake manifold leak.
connected in series with No. 1 spark plug,
(4) A vacuum of below 5 inches with a
should flash each time No. 1 cylinder is fired.
steady needle indicates an intake
When No. 1 cylinder is fired. When No. 1 cyl-
manifold leak.
inder is fired, the flywheel painted mark (DC)
(5) If the vacuum pressure is normal but
should align with pointer in flywheel housing.
drops at irregular intervals, sticking
With the engine operating at idle speed, the
valves, rich or lean carburetor mix-
light should synchronize with the alignment
ture, or defective spark plugs is indi-
of the painted mark and pointer. Adjust igni-
cated.
tion timing as follows:
(6) If the vacuum pressure is normal when
(1) Remove wire from No. 1 spark plug
when the engine starts but drops
terminal and connect one lead of neon
gradually, the exhaust system is prob-
light to wire and the other to the plug
ably defective or the muffler is re-
terminal.
stricted.
(2) Start engine and operate it at idle
(7) If the vacuum pressure is normal but
speed. Direct neon light flash at hole
drops at regular intervals, defective
in flywheel housing and inspect posi-
valves, or a leaky cylinder head gasket
tion of flywheel painted mark in rela-
is indicated.
tion to pointer in flywheel housing
hole.
(3) Adjust distributor as noted in a(5)
above.
a. General Method.
(4) After adjusting timing correctly, and
(1) Ignition timing should be set to fire
with neon light still connected, accel-
No. 1 cylinder at TDC (top dead cen-
erate engine rapidly from idle speed
ter).
and watch flywheel mark movement.
(2) Remove No. 1 spark plug and rotate
If the spark advance is working cor-
engine slowly until timing mark (DC)
rectly, the mark will move counter-
on flywheel alines with pointer in fly-
clockwise on the flywheel when ac-
wheel housing (fig. 6).
celerating the engine and recede to its
(3) Remove distributor cap. Distributor
original position when engine is de-
rotor should be in position for firing
celerated to idling speed.
No. 1 spark plug.
(4) Remove distributor rotor and seal
21. Cylinder Head
plate. Turn cam counterclockwise to
a. Removal (figs. 4 and 5).
remove backlash and adjust position
of distributor so that breaker points
(1) Drain cooling system (para. 32a).
AGO 6217A
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