1938 LaSalle Production - GM Heritage Center

new plugs if the old plugs are badly worn. A. C. Spark
Plug Model 45 is recommended for LaSalle V-8 cars.
Cleaning the timer contact points in the distributor and
setting to a gap of .012-.018 inch. Replace contact points if
they are badly worn.
Retiming the ignition to the timing marks on the harmonic
balancer at the front of the engine.
Carbon and Detonation—Most automobile owners
have been taught that a detonation or "ping" in the engine
is an indication of an over-advanced spark or of carbon in
the engine, and probably the latter. While this is true, the
following supplementary information must be included when
considering "ping" in any high compression engine.
On cars with high compression engines, slight detonation
occurring on rapid acceleration at low speeds and disappearing
at about 15 miles per hour, is normal and indicates that
the engine is performing at top efficiency. Detonation at
higher speeds can be eliminated by checking and correcting
the following:
Grade of gasoline used—The LaSalle V-8 engine is designed
for use with 70 octane gasoline (regular). Gasoline
of a lower rating may be used safely, but in this case the
ignition timing must be retarded to a point where the engine
will not knock.
Over-lean mixture—This may be due to ah incorrect
carburetor adjustment or to an obstruction in the fuel feed.
Spark plugs—One or more faulty spark plugs will cause
pre-ignition in their respective cylinders. Replace these
with A. C. Model 45 spark plugs.
Accumulation of carbon—Accumulated carbon must be
removed by scraping after taking off the cylinder head.
Removal of carbon by burning is not recommended.
Carburetor—The only adjustment required by the
carburetor is the idling adjustment.
The idling speed should be set with the throttle stop
screw to the equivalent of 6 miles per hour. The two idle
needle valves should then be adjusted until the engine runs
smoothly. These adjustments must be made when the engine
is hot.
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