Evening star., 1925-11-01
AUTOS SERIOUS ILLS
ARE EASILY PbEVENTABLE
Sudden Development of Major Maladies
May Be Thwarted by Slight Attention
to Early Symptoms.

I to reach q conclusion by safe route.
1t is evident that if pieces of car
! bon have accumulated around the seat
/ of an intake valve that valve will not
/ close tightly. thus allowing an escape
! back into the intake manifold for the
! gas when compression commences.
( Carbon around the exhaust valve will
offer just az good an escape. the only
difference being that the gas vapor
goes out through the exhaust and
thus represents Il double loss. 1t can
never be used again in the same
engine.
1t is also evident that if either one
OF these valves happens to stick open
during the cranking process the
vapor will escape rapidly, thus reduc-
ing the compression TO Il point where
the piston, in travelling upward on -
compression stroke, will show scarcely
any resistance. Whether or not this
, Is the case can he determined by re-
, moving the valve cover plates and
noting the position of the valve stems.
When the respective cylinder is under
compression both valves should be
closed. n position In which there
should be no noticeable clearance be-
tween the valve tappetS and the end
of the valve stems other than a nor
NAL clearance.
ENtfa Clearance Normal.
While in an engine that has had
attention for several months this
clearance may be greater than the
thickness of visiting card or what
ever guide the reference book for the
particular make of car recommends,
extra clearance may be normal for
the particular condition of the engine
if the same is found to be the case
with the valves for the other cylinders.
Excessive valve clearance all around
indicates that all valves are not seat
ing tightly. This means lung leak
age" and consequently waste of
power. To give the lung test" to
best advantage it is important to do
the hand cranking after the engine
has been thoroughly warmed up. for
the test should show how the power
plant breatheS when it is running
normally, not when cOngealed oil and
contracted parts are likely to miSlead
the owner. Valves that show too much
clearance when cold may show too
little when hot. This might mean
loss of compression during normal
running, and perhaps excessive COM
preston when cold.
In view of all these possibilities of
leakage of vapor. however. it is
usually not evident TO the motorist
that the principal cause of his uneven
compression may be due to worn piS-
ton rings or cylinders worn oval. Thus
he is likely to jump TO a conclusion
regarding the~~valves before consider
ing a more serious symptom.
This point calls for a little head
work rather than physical effort. II
cylinders Nos. and of a six cylin-
der engine, let us say. show excessive
ly low compression as compared with
the normal for the engine we may
assume leakage of vapor past the
piston rings into the crankcase. AS
Stunning this. it is also fair TO presume
that there would be a reverse leak
age from crankcase to cylinders
which would mean that in Nos. 3 and
8 spark plugs should foul more readi-
iy than those in the four other cylin-
ders.
Oil Consumption Grows
If the motorist has Kept records OF
supplies purchased for the car. and
if this condition be true, he will find
that his oil consumption has increased
a little. There may also be undue
smoking either from the exhaust or
breather tsibe, or both. There may
be a piston slap in the engine.
II 50. he has doubtless discovered
through the test that his cylinders
need reboring. or. in any case, that
new rings are needed. But if, on the
other hand, no such symptoms are Oh
served he is justified in suspecting
that valves need regrinding.
In a test of this sort it is very
important to see that the spark plug
of the cylinder being inspected is tight
and that the respective pet cock does
not leak To make the test without