Noisy Operation Of V-8 Valve Silencers - Cadillac 1937 LaSalle VVI Information

87
E N G I N E
T h e dash pot cylinder below the plunger is kept
full of oil and prevents the plunger from sliding
down into the cylinder when the valves are in
operation. The clearance between the. plunger
and the cylinder, however, is just enough to
let the plunger move down slowly, to compensate
for expansion as the engine heats up. A small
poppet valve opening downward in the bottom
of the plunger permits o i l to enter the chamber
below the plunger, providing silent valve operation
at all times.
22. Noisy Operation of V-8 Valve Silencers
N o i s y operation of the hydraulic valve mechan-
ism used on series 37-50, 60, 65, 70 and 75 engines
may be due to:
1. Plugged or loaded o i l filter.
2. Incorrect o i l level.
3. Improper oil pressure.
4. Weak valve lifter plunger springs.
5. D i r t y , scored or worn valve lifter parts.
Loaded Oil Filter—The o i l filter is the first
thing to be checked in case of noisy valve opera-
tion on 37-series V - 8 engines. A plugged or
loaded oil filter will not provide proper protection
to the valve silencer mechanism and may be a
contributing factor to noisy valve operation. If
such a condition is found therefore, the filter
should be replaced as the first step toward cor-
rection of the trouble.
Incorrect Oil Level—The level of the oil in
the engine is another important factor relating
to quiet valve operation. T h e o i l level should
never be above nor mere than one quart below
the 7 quart mark on the o i l level indicator. If
the level is too high, foaming may result; if the
level is too low, air may enter the p u m p inlet.
In either case, noisy valve action will result and
it is, therefore, an important item to check when
such trouble is encountered.
Improper Oil Pressure—Correct o i l pressure is
also an important factor to be checked in case
of noisy valve operation. E x t r e m e l y high pressure
may lift the entire hydraulic u n i t against the
plunger spring, permitting excessive plunger
movement and wear. L o w pressure permits oil
•relief leakage between the plunger and cylinder
to exceed the oil feed through the ball check
valve.
If the valve action is noisy after the o i l is hot,
determine the o i l pressure at the silencer pipe.
Pressure here should be 3 to 5 pounds when gauge
on clash reads 12 to 15 pounds.
Trouble w i t h the o i l pressure usually results
from a leak somewhere in the oiling system, a
stuck or improperly operating o i l pressure relief
valve, or scored and faulty operation of the o i l
pump. Correction, of course, should be made
by eliminating any leaks in the oiling system,
and replacement of any defective parts as the
case may require.
Weak Valve Lifter Plunger Springs—In some
cases, noisy valve operation may result from
weak valve lifter plunger springs which permit
excessive plunger movement and wear. If such
a condition is thought to be the cause of the
difficulty each valve silencer unit should be
checked as follows:
1. R e m o v e the four valve lifter assemblies.
2. Disassemble unit and thoroughly clean each
assembly so that each plunger and cylinder is
entirely free from o i l .
3. Carefully dry each part and reassemble unit.
4. C h e c k the pressure required to compress
each plunger spring, dry.
If the strength of these springs is such that less
than 6 or 7 pounds is required to compress them,
the hydraulic unit should be replaced. T h e valve
cylinder and plunger are mated and should be
replaced as a unit.
D i r t y , Scored or W o r n Valve Lifter Parts —
T h e following are further causes of noisy valve
operation on 37-series V - 8 engines:
Single noises—-A recurring tap or click s y n -
chronized w i t h the valve action indicated trouble
in single silencer units, which should be disassem-
bled and inspected for
1. S t i c k i n g mechanism.
2. D i r t , p i t t i n g or incorrect clearance between
plunger and cylinder.
3. Operating clearance between plunger and
valve stem.
Stic/ting—resulting from dirt or foreign par-
ticles is the most likely cause. It can be corrected
by thorough cleaning of i n d i v i d u a l . parts after
disassembly by wiping with a soft cloth and
washing in gasoline.
A stuck ball check valve may be unseated with
a small blunt tool, after which the cylinder should
be washed thoroughly in gasoline.
A i r pressure may be used to dry parts but the
nozzle should be held at least two inches away.
T h e engine o i U p a n should always be removed
and cleaned, and the engine flushed when dirt
has been responsible for sticking, otherwise the
condition may recur almost immediately. T h e
oil passages in the valve lifter brackets should also
be thoroughly cleaned.
P i t t i n g and Scoring-^-of the surfaces may
cause sticking. T h i s may result from gritty
particles, excessive wear or damage during installa-
tion. T h i s condition requires replacement, of the
hydraulic u n i t (cylinder and plunger). It is not.
necessary to replace the valve lifter body.
Note Slight scratches on the valve lifter body
have no effect on the operation of the
engine or the valve silencers.
Incorrect clearance—between the cylinder
and the plunger is usually caused by mismating of
parts. T h e parts of the hydraulic unit—cylinder
and plunger—are carefully fitted in production
and are not interchangeable.