El Paso herald. (El Paso, Tex.) 1901-1931, 1918-01-19
lie automoblle englne b

l ike q human being In one par
= ticular. its functional well be-
ing IS largely dependent on a resplr-
atory system. By this expression. we
mean that part Of its mechanism that
has to do with breathing In Of the
fuel yapor and the expelling OF the
burned gases after combustion has
taken place. The respiratory function
OF the engine IS controlled by the
valves. II the valves which permit
the fuel TO enter the combustion
chamber do not perform their work
properly. much OF the power OF the
motor VIII obviously be lost. Again
it Is Just as important to get the
burned gases out Of the way after
combustion. for their continued pres
encs in the combustion chamber viii
contaminate the fresh fuel. Granting
then the Importance of the valve sys-
I tom, brief study OF the unit Its
common failings and how TO remedy
them may be interesting and helpful
To begin with here are five definite
types OF valve gears. The most pop
ular type consists OF a single cam
shaft. operating. pushrods, which
directly control the valves. This is
I the type that is used on L-head en-.
ines, by far the c0mmonest type Of
power plant The next type is the
velve-in-head. which means that the
valves are located In the heads OF the
cylinders, the operation being
achieved by means Of vertical rods
and rocker arms These rocker arms
are merely pivoted levers, operated
from vertical rods, which extend up
from a push rod. driven by an ordi-
nary camshaft- The next valve type
is known as the T-head, which oper-
ates on the same principle as the
L-head, but has two camshafts. one
for intake and the other for exhaust
valves. The fourth type also has
valves IN the heads OF the cylinders
but the camshaft is placed on top Of
the cylinders instead Of being IN the
crankcase. The final type is the
sleeve valve, which are simply ports
in sliding sleeves which are actuated
BY eccentric shafts. corresponding to
the camshafts OF ordinary practice.
Operation of Valves.
Most car owners understand some
thing OF the way in which valves are
operated, but we shall describe the
operation briefly. The camshaft is
geared to the crankshaft and as II re-
wolves the cams are brought into con-
tact with the valve litter. which IS
cylinder Bit OF steel. moving up and
down within q guide. AS the litter Is
forced upward II pushes the valve
open against the resistance OF
spring. When it reaches its limit Of
upward movements, il sinks down
again and the spring closes the valve.
Obviously the position and size OF the
cams and other parts OF the valve
gearing must be accurately deter
mined 10 keep the valve open for just
the proper length OF time. Also the
valves must open at exactly the right
IN Ia hnn Ion faN
the piston. II viii be evident that
wear In certain parts OF this valve
system viii cause arrangement or
the entire operation OF the respirra-
Tory system Of the engine.
The modern tendency in engine de-
sign Is to keep the entire valve
mechanism exposed to perpetual
spray Of oil In some designs pipes
are provided, but In others the valve
system is located inside the crank
case, where II gets splash fabrication
from the connecting rods. AS a result
Of this tendency the wear and con-
seQuent noisy operation Of the valve
system. which used to be almost uei-
versal. has been largely eliminated. /
nevertheless, the average car owner
does not give his valve system the
Fare or rather watching that II needs
and small things often develop into I
big failures for lack OF a small at |
teDcon in time.
Leakage of Oil.
For instance. it Is not uncommon |
TO find an excessive leakage Of oil |
own the sides o. the valve. This is ]
caused BY wear Of the valve stem or
stem guide, usually brought about by
insufficient fabrication. Something
may have prevented oil from getting
to the mechanism and the result has
cen excessive and rapid wear. or
he condition may be caused by the /
fact that the valve is pushed side
ways whenever it is raised, because /
Of bent stem, worn tappet or stem
oottom- II frequently happens that
me stem Will be struck at one point I
only, inducing excessive side thrust. /
wearing the valve stem guide. When |
the guides have been worn In this |
way II Is possible 70 ream them out !
and fit valves with oversize stems An |
repair IS to fit bronze !
bushings in the guides, II these are |
not already used. Whenever the |
valves are taken out for any reason. |
they should be examined for bent |
stems and for play in their guides. IN |
Inspecting the stems It IS best TO use !
a steel square, as the eye often fails |
TO detect a slight bend.
Another valve trouble IS wear OF |
the tapDets. which causes a slapping /
in their guides, a very annoying con- |
dition, the existence OF which may be /
detected by shaking the tappet with /
the fingers, after the spring pressure /
has been removed. The methods Of I
overcoming this slapping are almost /