Tune-Up And - Chevrolet Corvette 1963 Repair & Tune-Up Manual

Performance Maintenance
TUNE-UP PROCEDURES
This section gives specific procedures on how
to tune-up your Corvette. It is intended to be
as complete and as basic as possible. Those
who are familiar widi die steps involved in a
tune-up may wish to slap die following pro-
cedures and use die generalized section in
chapter 10. However, it is felt that nothing
would be lost by first reading over tins sec-
tion. Perhaps the best procedure to follow
would be to read botii sections before start-
ing your tune-up.
Spark Plugs
A typical spark plug consists of a metal shell
surrounding a ceramic insulator. A metal
electrode extends downward through the
center of die insulator and protrudes a small
distance. Located at the end of the plug and
attached to die side of die outer metal shell
is the side electrode. The side electrode bends
in at a 90° angle so diat its tip is even witii,
and parallel to, the tip of the center elec-
trode. The distance between diese two elec-
trodes (measured in tiiousandths of an inch)
is called the spark plug gap. The spark plug
in no way produces a spark but merely pro-
vides a gap across which the current can arc.
The coil produces anywhere from 20,000 to
40,000 volts which travels to die distributor
where it is distributed through die spark plug
wires to die spark plugs. The current passes
along die center electrode and jumps die gap
to die side electrode, and, in so doing, ig-
nites die air/fuel mixture in die combustion
chamber.
SPARK PLUG HEAT RANGE
Spark plug heat range is the ability of die plug
to dissipate heat. The longer die insulator (or

Tune-Up and

die fartiier it extends into die engine), die
hotter the plug will operate; the shorter the
insulator die cooler it will operate. A plug tiiat
absorbs littie heat and remains too cool will
quickly accumulate deposits of oil and carbon
since it is not hot enough to burn diem off.
This leads to plug fouling and consequendy
to misfiring. A plug diat absorbs too much
heat will have no deposits, but, due to die
excessive heat, die electrodes will burn away
quickly and in some instances, preignition
may result. Preignition takes place when plug
tips get so hot diat diey glow sufficiendy to
ignite die fuel/air mixture before die actual
spark occurs. This early ignition will usually
cause a pinging during low speeds and heavy
loads.
The general rule of tiiumb for choosing die
correct heat range when picking a spark plug
is: if most of your driving is long distance,
high speed travel, use a colder plug; if most
of your driving is stop and go, use a hotter
plug. Original equipment plugs are compro-
mise plugs, but most people never have oc-
COLDER
Spark plug heat range, the higher the number the
hotter the plug
HOTTER