1938 LaSalle Production - GM Heritage Center

Valve
Mechanism
All Cadillac-built engines are of L-head design. Intake
and exhaust valves are maintained in constant, accurate
adjustment by hydraulic valve silencers or lash adjusters.
These eliminate tappet noises frequent in all engines
without automatic valve adjusters and particularly
frequent in those of overhead valve design.
Service experience proves that 75 per cent of the
cause for valve grinding is incorrect valve tappet
clearance. This results in overheated valves and seats,
causing leakage which decreases power output and increases
fuel consumption. Valve silencers in all Cadillacbuilt
engines eliminate this cause for service and operating
expense by maintaining zero clearance under all
conditions, thus prolonging valve life over other
engines. With but one exception Cadillac and LaSalle
are the only cars under $3,000 equipped with these
owner-saving instruments.
Hydraulic valve silencers permit the use of mushroom-type
followers and cam contours such that a fast
opening and closing of valves is realized for greater
power and performance.
These silencers are extremely costly instruments and
have an accuracy of precision in manufacture equivalent
to the world's finest and most expensive watches. Their
operation is hydraulic, utilizing oil supplied under
pressure by the engine's lubrication system. The
silencers automatically keep all lost motion out of the
complete valve mechanism under all conditions.
Valve seat inserts are unnecessary in Cadillac engines
because of the especially hard cylinder block material.
Inserts are required in other engines to resist the
hammering action of valves in their seats when an
inexpensive soft iron block material is used. Also, in
the Cadillac design, heat from the valves escapes
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