Letters and Miscellanies

By Staff
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Get the Right Plug

After reading the Stationary Engine List by Helen French in the
December 2001 issue of Gas Engine Magazine, I find there
needs to be a lot of enlightenment about spark plugs. I have been
advertising and selling obsolete and vintage spark plugs for
somewhere around 15-20 years in GEM. I have been supplying spark
plugs to restorers and collectors in all phases of the hobby for 20
years and have an extensive library and computer files dedicated to
this purpose.

I am also the reference for Champion Spark Plug Co., Autolite
and AC Flint customer service referrals for obsolete spark plugs,
and I talk to their service personnel on a fairly regular basis. I
enclose a page of spark plug information when I send out inquiries,
and 1 think the information in it could be of benefit to GEM
readers.

First, let’s define the problem with the new spark plugs.
When automobiles became computer controlled, the spark plug did not
have to have the bottom of the insulator glazed. New cars have fuel
injection, and the computer will not put enough gasoline into the
cylinder to flood it. It injects fuel into the cylinder and says,
‘I will not put any more fuel into the engine until it
fires.’ Then, it fires the cylinder with 40,000 volts. If
something happens to this computer control and too much fuel is
injected into the cylinder, and the engine floods, this vehicle
will not run right until you have replaced the old plugs.

What has happened is the trash gasoline that has been forced on
us contaminates the spark plugs because they are not glazed on the
bottom. However, when was the last time you flooded a
computer-controlled vehicle? More than likely, never.

Now, these old engines do not have a computer control, and if
your carburetor is running rich or you flood the engine, the same
thing happens. The bottom of the insulator where it fires the
engine becomes contaminated and becomes junk. The point coil or
magneto ignition does not have 40,000 volts to fire the spark
plug.

The solution to this problem is to find the spark plugs that
were manufactured prior to the time that they quit glazing the
bottom of the insulator. In those engines that used 1/2-inch pipe
thread spark plugs or 7/8-inch by 18 thread plugs, the best deal is
to try to buy spark plugs that come apart so the insulator can be
taken out and cleaned with WD-40, kerosene, diesel fuel, or other
things that will remove the glaze on the bottom of the insulator.
In any case, do not sandblast or glass bead them. This removes the
glaze and you have a short plug life just as though you had
purchased one of the newly manufactured spark plugs.

Those plugs that do not come apart, but are glazed on the bottom
of the insulator, can be put in a can of the same material
mentioned above and set over night. Then brush the carbon and oil
out of them with an acid brush or other small brush. After cleaning
them, blow them off to remove the excess cleaning liquid and your
are ready to run again.

I cannot emphasize enough that spark plugs should not be
sandblasted or glass beaded. Also, to get any length of life in the
old engines they must have an insulator that was glazed on the
bottom.
Donald McKinsey , P.O. Box 94 Wilkinson, IN 46186

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