Page 20 - Combined_141_OCR

CLEANING RACING PLUGS

Providing heat range selection is correct, gap wear is neg­ rounding of the electrode edges which results in an increase
ligible in racing applications* ...lead deposits have little in voltage requirement. It should be noted that filing of the
opportunity to form ... fuel deposits do not congregate .. . electrodes to obtain bright, sharp edged surfaces Is an essen­
and methanol or methanol-nitro mixes are exceedingly clean­ tial final step in servicing plugs. Blow out all filings.
burning.
The ceramic firing end of a racing plug is not glazed as
is popularly assumed . . . consequently, abrasive cleaning
cannot remove any glaze. Careful cleaning with a well-main­
tained plug cleaner will not shorten or “rough-up” the nose
altering heat range. It is imperative that the abrasive com­
pound be fresh (used compound is of powder-like consistency
and gives off smoke-it will not clean spark plugs). Most
service stations and garages do not drain the abrasive fre­
quently or replace worn out jet nozzles. They merely dump
new abrasive into the unit without draining the old. Such
practice makes cleaning extremely inefficient.
Spark plugs wetted from oil or fuel should not be blasted
in a cleaner. They must be completely degreased and thor­
oughly dried before blasting. Do not use carbon tet to
degrease a plug. Lacquer thinner or Stoddard solvent is pref­
erable. The plug must be dry.
It is most important to wobble the plug continuously dur­
ing cleaning —do not hold the plug in a stationary position
-a three to four-second blast should be sufficient to per­ Spark plug cleaning can greatly lower the expense of
fectly scour the insulator. The firing end should be vigor­ drag racing. The environment of drag racing imposes more
ously air blasted free of all abrasive. The area between the severe demands thermally and electrically upon the spark
center electrode and the nose should be carefully inspected. plug than any other form of racing... reasons being the
plugs must run the entire spectrum of heat range from foul­
*Possible exceptions are 12-24 hour endurance events. ing to near preignition at constant wide-open-throttle ac­
“J” or cut-back gaps may erode perceptibly. A closer celerations. This condition causes a very rapid rise in voltage
initial gap setting is recommended. requirements attributable to the rapid increase in compres­
sion pressure when the throttle is open. As the spark plug
electrodes have not had time to heat to high temperatures,
the voltage requirements of the spark plug is greatly in­
creased.
It is not unusual in a slightly off tune engine to experience
an increase in elapsed time and a decrease in top speed
after several consecutive runs ... despite a visual examina­
tion of the plugs revealing no deposits or contamination,
servicing these plugs in a well-maintained cleaner will give
the same results as running with new plugs. Never wire
brush a spark plug, as metallic deposits will impregnate the
insulator and cause misfiring.
FILE I
“Regular,” “J,” and “Y” gaps should be opened wide
enough (bend only the side electrode) to permit vigorous
filing with a point file of all sparking surfaces. This lowers
the voltage requirement of the plug. The plug can then be EXTRA HORSEPOWER FROM A SPARK
regapped to specifications. Do not file “fine-wire” plugs. A spark plug draws only the voltage it requires. If the
“R” types, of course, cannot be filed. “R” gaps, however, a.ailable voltage is adequate, the cylinder is fired ... the
do not fire across parallel surfaces . . . they fire across excess voltage is not used.
sharper corners, consequently, the voltage requirement is A claim of an appreciable gain in horsepower due to the
less. In addition, “R” gaps are set to closer gap tolerances -stallation of “revolutionary” plug designs or ignition sys­
than “open electrode” types. tems is usually unfounded. This gain in the true connotation
Many very successful racers have a definite preference for is recovered horsepower. Maximum horsepower has been
cleaned plugs-preferring them to new spark plugs. Cleaned restored to the engine by adequate ignition, enabling the
plugs are accepted practice with airlines, executive, and RPM level to be re-tailored to the camshaft range and ex­
private aircraft. When the cleaning process is performed haust tune.
carefully on well-maintained cleaning units (containing fresh (If the engine gained 18 horsepower on the dyno,
abrasive and new jet nozzles), the results are comparable this horsepower was already in the engine ... the
to new plugs. Buy a new can of abrasive and change the 18 horsepower was not supplied by the new igni­
old cleaner jet. Instructions for re-jetting (and a new jet) tion components.)
are in the can. Measurable horsepower gains are generally derived from
Spark plugs can be expected to require progressively precise ignition timing (“spark curves”). Spark plug gap
greater voltage as the sharp corners of the electrode erode style and location can also give significant improvements in
away and become rounded. While abrasive cleaning removes horsepower and engine responses.
most deposits from the insulator, it may cause a slight
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