1938 Cadillac V16 - GM Heritage Center

14 Cadillac-LaSalle Preliminary Service Information
The breaker mechanisms for both of these circuits
are, however, located in the same distributor
housing—the left-hand one. The two breaker
arms, although separate electrically, operate on
the same eight-lobed cam, as did the 37-90 breaker
arms. The right-hand distributor unit serves only
to direct the current to the spark plugs in the
right-hand block. (See Fig. 12).
The ignition coils are mounted on a bracket
attached to the radiator upper tank, and held
together in a die-cast base into which the ignition
lock cable passes. The two distributors are
mounted at the front of the engine and are driven
by a single gear from the camshaft. As viewed
from above, the left hand distributor rotates clockwise
and the right-hand distributor counterclockwise.
The two condensers are mounted on
the outside of the left hand distributor.
Fig. 11. The correct generator drive adjustment on 38-90
is determined with a spring scale as shown.
If it is necessary to replace one of the dual belts,
both belts must be replaced, and the new belts
that are installed must be a matched pair secured
from the factory Parts Division. Only belts properly
matched for length at the factory will operate
satisfactorily in the V-16 engine.
The friction drive for the generator seldom reuires
attention in service, but when readjustment
3oes become necessary, it must be made accurately
with a spring scale. Before attempting this adjustment,
make certain that the fan belt is correctly
adjusted, and then proceed in the following
manner:
The high tension ignition wiring from distributors
to spark plugs is concealed and protected
by metal conduits. The distributor head terminals
are of the thrust type. The 14 mm. spark plugs
(A. C. Type 45) require a setting of from .025 to
.030 inches, the same as the V-8 plugs. The contact
point gap is from .0125 to .0175 inches.
The cylinders are numbered from the front by
the usual Cadillac method, with the left front
cylinder designated No. 1, the right front, No. 2,
etc. The firing order is 1, 4, 9, 12, 3, 16, 11, 8, 15,
14, 7, 6,13, 2, 5,10. Ignition timing marks appear
on the harmonic balancer at the front of the engine.
Attach the spring scale to the rim of the ventilating
blower at the rear of the generator and pull
it out tangent to the rim. The adjustment is correct
when a pull of 9 to 12 pounds is required to
slip the generator drive. Check this adjustment
at several points on the circumference of the
driving drum to guard against errors due to possible
eccentricity.
The tension of the wheel against the drum is
controlled by the set screw shown in Fig. 11. To
increase the tension, merely turn down the set
screw. To decrease the tension, the set screw must
be backed off and the mounting bracket tapped to
force it downward.
Re-check the tension at several different positions
after each readjustment.
Ignition System—The ignition system is new,
yet similar to the 37-90 system. The ignition circuit
for each bank of cylinders is entirely separate:
two coils and two condensers are used, and two
separate distributor units direct the high tension
current to the proper spark plugs.
FRONT
Fig. 12. Ignition circuit diagram, 38-90 engine.