Evening star., 1922-12-24
THE OWNER-DRIVER'S
COLUMN
Test the Timing Of Your Engine'a
Valves.

Test the Timing Of Your Engines
Valves.
In order to cause an explosion In an
engines cylinder the gases must first be
OF the inlet valve while the piston Is on
the outward or intake stroke. The pis-
ton when moving out of the cylinder
produces a vacuum in the cylinder and
the air rushes in through the carbureter
and manifold to fill this space. As soon
as the crank reaches outer dead center
che piston ceases to move out and as
the crank passes dead center OF its ro-
tation the piston moves back into the
cylinder. The valves must now be
closed: the gases are trapped and COM
pressed into a small space by the re-
turning piston. This is the second or
compression stroke. Just as the piston
has reached the end of this stroke and
the crank commences to draw the pis-
ton over dead center the explosion must
take place. This drives the piston out
with great force. producing the power
stroke" or third stroke of the piston's
cycle. The explosion leaves the cylinder
full Of burnt gases and while the piston
is sent into the cylinder by the whirling
crank the exhaust valve must be held
open for the escape Of the exhaust gases.
Such is the action of the four-cycle
engine.
Timing the Inlet Valve.
To the average man it would appear
that the inlet valve must open at the
beginning of the intake stroke and close
at the end Of it, that both valves remain
closed during the compression and
power strokes and that the exhaust
valve be opened at the beginning Of the
exhaust stroke and closed at the end Of
It.: This is. however. not the case:
While the crank is passing the dead
centers in its rotation the piston is
practically standing still. Then as the
crank leaves dead center the piston
moves with it. This fact is made use
of in valve timing. When the crank is
beginning of the suction stroke. the in
take valve is not opened until the piston
commences to move out: that is when
the crank has passed dead center by
about seven degrees. Then when the
crank is passing over outer dead center
intake valve is left open till the piston
has started on the return stroke or till
the crank has completed from twenty
to thirty-eight degrees Of the compress
sion stroke. This is done because the
gases which rush into the cylinder with
considerable force when an engine is
running will continue to crowd into the
cylinder in spite of the fact that the
piston has completed its stroke. More
gas in. the cylinder, Of course. means a
stronger explosion.
Timing the Exhaust Valve.
The exhaust valve is opened long
before the piston has reached the
outer or dead center of the power
stroke and is held open while the
crank finishes this stroke and all Of
the next. which is the exhaust stroke.
This is necessary to allow the ex-
fause gases sufficient time to escape
so as to clear the cylinder of all USE
less gases before the next intake
stroke. If there is any pressure left
in the cylinder when the piston starts
on the intake stroke. suction will he
weakened. the gases drawn in will
be insufficient and weak engine oper-
alton will result. The exhaust valve
should open when the crank reaches
center on the power stroke and the
valve must be held open till the crank
has passed inner dead center on the
intake stroke. That is. tho exhaust
closes just as the intake commences
to open.
To test the timing of the valves
the crank should be visible. If the
engine has an exposed fywheel. the
dead center position OF he crank IS
usually found by bringing a mark on
the hywheel opposite the trammel
point or mark on the cylinder cast
ing When the flywheel is inclosed.
removing the oil pan from the crank
case will reveal crank positions.
AS general thing. however. it will
be unnecessary to examine the tim
ing as closely as this. If the actual
meshing of the gears has not been
changed by an incompetent workman,
the timing is likely 10 be correct. as
is in the tappets or valve lifters
where we must look for trouble.
The ends of the valve stems and of
the valve lifters will continually
wear off. II this wear is not taken up
the valve will open late and close too
early. In the inlet valve this will
mean dearth of gas in the cylinder
and with the exhaust valve it means
incomplete scavenging, leaving burnt
gases in the cylinder at the end of
the exhaust stroke. Overheating. in
creased fuel consumption and lack of
this. All this trouble can be remedied
by keeping the "tappets" or valve
lifters properly adjusted. These ad-
justments should not be left to the
the owner who takes
pride in his knowledge of his car will
The Battery Deserves Extra Care In
Cold Weather.
The little black box Of mystery"
as the storage battery is called by
some people. needs a little more con-
sideration in winter than in summer
Two dangers must be guarded against
by car owners: the first is freezing
the battery. and the second is over
work caused by lengthy cranking Of
a cold motor.
The first danger can be counter
acted by keeping the battery fully
charged. The following table shows
the freezing point OF electrolyte Of
various specific gravity readings:
Hydrometer Reading. Freezing Point.
Fully discharged, 1.l60 .1s' above zero
u discharged. 1.225 .3so below zero
}. discharged. 1.2GO go below zero
Fnllv chrS'd. t2S0-1 800 80 to go below zero
1t requires more than twice the
power to crank a thoroughly cold
engine than is necessary to spin the
same engine when warm. Therefore.
a battery must not be asked to do
this very long at time. Have the
engine ready for starting before step
ping on the starter switch. Pull the
primer properly, open the throttle
and retard the spark. then step on
the pedal