The Washington herald., 1917-10-07
'rr!HOD OF TIMING AN AUTO engine
is GIVEN BY AN EXPERT Instructor
B. NJ Ikert Explains What to Do When Cam
shaft and Magnetic Are Not Marked.
Four as Example


presume that the engine is reas-
sembled with the exception OF the
timing gears and magnetic drive. The
latter might be In the form Of chain
or gears like those that drive the cam
shaft. The first thing to do Is to place
the piston Of cylinder No. al. the top
dead-center point. II the engine is
fitted with spark plugs IN the center
OF the combustion chamber wire can
be inserted In the hole and by slowly
turning the engine over the wire will
rise with the piston and when II ceases
to rise. obviously the piston is as high
up IN the cylinder as it can go.
A better way would be to remove the
plate on the bottom OF the crankease
and note the position OF the crank
shaft. When the cranks are in q per-
feet vertical line. so that No. Is up.
the piston will be in the top at dead
center. II the engine is of the L-head
type with the plugs and pet cocks over
the valves lt/will be more difficult 10
find the top position OF the piston. but
a small electro light can be brought
close to the spark plug hole and the
light Will show the piston as 1t begins
to come near the top. BY carefully
N's- '+Aaie NhV NheilAC anu "atNlAAbS Ailt
piston. Il car be correctly placed
With the vslve-in-head engines, Il the
valves are held in cages, the latter
can be taken out and the piston
watched through the opening.
With the piston Of No. cylinder In
the correct position. that Is, as far up
as ii will go, the next step Is to get
the valves placed correctly for It, In
the first place the piston is supposed
to be at the top compression center.
and In order that the gas might be
compressed the valves will have to be
closed. Before tackling the valves.
make prick punch mark on the fly
wheel rim at the extreme top. Make
a similar mark on the engine crank
case opposite the one on the fiywheel,
so that both marks will be coincident
with line drawn vertically through
the center OF the fi.wheel. These
marks are made so that II the engine
has to be refined later on the hywheeI
can be revolved so the marks register
and the operator will know that the
piston OF No. /. as well as that for No.
4. is at the top of the stroke. The fig-
ures i and 4 should be stamped near
the marks to show what pistons are
on top.
A mark made at a point diametri-
cally opposite the first on the nywheel
would show that pistons 2 and are
at the top when 1t registers with the
punch mark that is on the engine base
Time to Operate Valve.
To get the time of opening and
closing Of the valves. rotate the cam
shaft in its normal direction and
watch the movement Of the valves in
cylinder No. /. There will be a time
when both valves are closed, and fur
ther rotation OF the camshaft will
cause the exhaust valve to open. The
latter does not happen Immediately,
however, for the piston will be on the
power or firing stroke. and the valves
must be kept closed until near the
end OF this stroke, when the exhaust
begins TO open to let out the burned
gases. Turn the cam shaft back to
where the exhaust and inlet closes
completely, with the cam for the lat
ter in the position shown in the dia-
gram.
Now slip the camshaft gear. which
Is twice the size OF that on the
crank shaft, back TO the cam shaft
~ Nh1N NAAC ACCNh Will the one
on the crank shaft. II there Is a diff
ferent form of drive for the timing
gears, such as a chain. II should be
connected with the piston and valves
In the position above After this is
done, the engine Will be timed cor
rectly in regard to the valves and
taken up.
Magnetic In Position.
The first thing to do is to put the
magnetic In the correct position; that
is, revolve the armature shaft By
hand until the breaker points are
about to separate. This separation
takes place when the fiber block on
the end Of the bell-crank comes in
contact with one of the cams on the
inside of the contact breaker box.
These cams are shown in the dia-
gram by the shaded portion. Re-
move the cover from the distributor
housing and note the position of the
distributor arm. II it is near or on
segment No. l 1t Is in the correct
position, otherwise the armature
shaft will nave to be rotated again
until these conditions are realized.
Make sure that the arm or lever on
the interrupter housing Is in the ex-
treme retarded position. This can be
done IL the magnetic has not been re-
moved from the engine base. by
placing the spark lever ON the steer
ing wheel in the retarded position.
Keep the magnetic in this position
and slip the gears in place so that
all mesh properly. In other words,
have the magnetic armature and dis
tributer correspond with those that
are shown in the diagram.
When the mechanism of the engine
and magnetic is brought together so
that the parts bear the relation as
Illustrated, and when the gears put
back, the engine will fire properly.
sometimes setting the gears one tooth
either way after timing will result
in better running.