Chevrolet Light - Page 35

and no more (fig. 40). This is approximate ly 1h turn of the
spring from its position when unhooked.
Engine Tune.Up
In order to enjoy the performance and economy whic h
Chevrolet built into the truck engine it must be kept prop-
erly tuned. Normally this service should be perfonned every
5,000 miles. A thorough engine tune-up requires the use of
special equipment not genera lly in the hands of truck owners.
For this reason it is advisable to have this service performed
by a Chevrolet dealer. However for the benefit of those
owners who perfonn many of their maintenance repair opera -
tions we will outline the operations which should be given
attention when tuning an engine.
Compression. Compression tests should be made before per-
forming tune-up operations to determine the necessity · for
interna l repairs-an engine with poor or uneven compression
cannot be successfully tuned.
Spark Plugs. Remove, clean and adjust (page 31).
Battery. Check state of charge by testing specific gravity
(page 58).
Battery Cables. Clean and tighten cable terminals.
Distributor: Clean and adjust distributor points. Inspect cap
and rotor (page 30).
Ignition Timing. Check and adjust ignition timing (page 31).
Fuel Pump. Clean fuel pump filter bowl and screen (page 28).
Air Cleaner. Clean air cleaner (page 26).
Manifolds. Tighten manifold bolts to guard against intake and
exhaust leaks.
Valve Clearance. Check and adjust valve lash to proper clear-
ance (page 23).
Carburetor. Adjust idling speed and mixture (page 24).
Cooling System. Tighten all hose connections. Check fan belt
adjustment and the cooling system for coolant leaks.
Road Test. After the engine is tuned the trqck should be road
tested for performance. During this test the octane selector
shou ld be adjusted for the grade of fuel being used. For best
performance and economy the octane selector should be set to
produce a slight "ping" upon acceleration at wide open throttle.
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