Nine Meadow Lane, North Caldu/ell, New Jersey 07006
The box under the table held strange looking objects with
porcelain tops. If these were spark plugs, I questioned why the
petcocks... and the springs... and the little windows. There was a
whole new world in that box and my bride of three months shook her
head at my lingering interest. The sign said '25 and 50'.
The vendor leaned over the table and said, 'They're all a
quarter'. I was hooked!
That started a 25 year hobby... and thankfully, it's just as
interesting today as it was then. Prices are higher, but new and
different spark plugs turn up at almost every meet. Spark plugs are
generally discarded when they are changed today, but most early
plugs could be disassembled for cleaning. And they were expensive!
A good spark plug sold for $1.25 in 1910, the same year you could
buy a colt revolver for $13.50 or a pair of shoes for about $2.50.
It was natural to save and clean spark plugs! They're still
hiding in barns and garages and part of the fun is digging them
So many different spark plugs were produced! Over 4,000
brand names are known to collectors. No doubt many were
'private branded' by the larger manufacturers, but between
1900 and 1925 there were probably 1,000 different companies or
individuals who manufactured or assembled them from parts.
In truth, the history of spark plugs parallels that of early gas
engines and automobiles. It was a marvelous era. Technical
developments poured out in profusion. Every manufacturer seemed to
have his own idea of 'improvement' and took it to the
marketplace with much fanfare. Early advertisements give a good
idea of what was available and also the competitive atmosphere.
Advertising was in its heyday and many ads made claims far beyond
reality; truthful or not, they make great reading. A friend
suggests, 'They had the ethics of weasels, helping themselves
liberally to each other's technology; if not patented, they
marked it patented just to claim superiority'.
The names themselves speak of the variety: Barney Google,
Bald Head, Spit Fire, Inferno, Blue Blaze, Fan Flame, Home Run,
Kantfoul, Sure Pop, Hire Fire, Bulls Eye, Ezekleen, Raccoon.
But it's the mechanical gadgetry that intrigues most
collectors. Some features had real value; others were destined to
oblivion as soon as the consumer passed judgment. Spark plug
collectors tend to classify plugs by their features; there were
primers, quick detachables, self-cleaners, breathers, visibles,
'intensified' plugs, series plugs, double-enders, and those
of special interest, perhaps because of shape or color.
Priming plugs were fitted with pet-cocks or valves for the
direct addition of a little gasoline or ether for cold morning
starts. Some priming cups were tapped into the sides of the plug
while others were mounted up top and primed through the center of
the porcelain. These 'top primers' often had brass funnels
and some allowed withdrawal of the center electrode for cleaning.
When polished, they really dress up an early engine.
In this day of improved gasolines, priming may be a lost art.
There is an oil field engine near Wooster, Ohio, that refuses to
start without a 'warm head'. On cold winter mornings, the
operator actually builds a wood fire under the overhanging
cylinder. I have often wondered if a priming plug wouldn't save
all that trouble.
'Quick Detachable' plugs could be disassembled without
tools while still in the engine. They generally had handles that
could be twisted to allow removal of the porcelain for cleaning.
Before reassembly, the cylinder could be primed right through the
plug body. Some were complex and beautifully machined; today, the
cost of manufacture would be absolutely prohibitive! Most had
shortcomings beyond their high cost; carbon deposits would soon
encrust sealing surfaces rendering them 'leakers'. The more
frail designs were subject to distortion, especially if the engine
man had arms like Popeye!
Spark plugs with external spark gaps or 'intensifiers'
were said to burn through oil on the points. Although
controversial, I am told that intensifiers really did work. The
coil had to produce higher voltage to cause 2 sparks in series. The
spark across the external gap allowed higher amperage to cross the
working points and the heavier spark improved performance in
oil-slinging engines. The theory is still applied today; modern
'ignition wires' are actually resistive carbon tracks...
they generally contain no metallic wire. Intensified spark plugs
often had little windows to observe the external spark and some had
magnifying lenses to improve visibility.
'Self-cleaning' spark plugs are among the most
interesting in terms of unusual construction. Some had fans for
electrodes which were said to rotate and present new firing
surfaces. They were supposed to produce a 'swath of flame'
and 'blow away the soot'. .. sadly, few worked. One
self-cleaner that may have worked is the Myers plug. It contained
about a dozen little porcelain balls that rattled about, dislodging
carbon deposits. The Wellman-Howe Push-Clean had a spring-loaded
center electrode fitted with a coarse-toothed file. By pushing the
electrode up and down, the file chewed off carbon buildup. The
Wellman Turn-Clean had a knife blade on the center electrode. By
lifting and turning, the blade was said to scrape carbon from the
porcelain. Some had ball bearings for electrodes that were caged to
maintain a fixed gap, but could roll and bounce about, cleaning
away carbon while the engine ran. The Schlect Sliding Gap plug had
a small metal 'bowtie' on the center electrode that could
slide up and down; the 'Movie' spark plug had a heavy
sliding electrode with spiral grooves to provide rotation. Alas,
not many lived up to the fanciful claims.
Visible spark plugs had translucent 'porcelains' or
clear glass windows to permit observing the color of the flame in
the cylinder. By adjusting the carburetor, the engine man could get
an efficient blue flame... but regrettably, few engines were up to
such scrutiny. The big straight 8 automotive engines were
particularly unresponsive. If the carburetor was adjusted to
produce blue combustion in the center cylinders, the end cylinders
usually burned orange. And if the end cylinders burned blue, the
central cylinders likely burned orange. These diagnostic plugs
simply exposed the inadequacy of carburetion! And that spelled the
doom of visible plugs. Still, these make fabulous plugs for running
an engine at night. The flash of combustion is a real
Breather plugs were designed to admit a little air during the
intake or suction stroke; the air was said to lean the mixture and
cool the points, saving gas and 'improving performance'.
The spring loaded inlet valves on used plugs are usually clogged
with oil and soot, telling of their shortcomings. Ironically, while
the virtues of 'cool points' were touted by some
manufacturers, other companies provided long reach electrodes to
ensure 'hot points'. The truth is that people didn't
know what they wanted, nor was there, a unified understanding of
what was best. Different brands of plugs actually provided
different 'heat ranges' and the engine man selected a
suitable plug by experimentation.
Another idea to improve combustion was to provide two or more
simultaneous sparks in the cylinder. If one spark could ignite the
mixture, two had to do it better. Some plugs had double gaps in
series; others were designed for engines with two separate spark
plugs in each cylinder, passing the hot lead to the second plug
before grounding the spark. 'Dual Ignition' plugs allowed
the choice of magneto or coil ignition at the operator's
'Coil plugs' had the coil built right on top of the
plug, doing away with the hot wire altogether. It is said that
early converts to mechanical power had a certain fear of
electricity.. . and being zapped by the spark plug wire surely
didn't help! Most coil plugs were used on marine engines where
absence of the moisture-sensitive hot lead was a real benefit.
Among the most unusual appearing plugs are the double-enders.
These had two 'working ends' at opposite ends of the
porcelain. When one end failed, the operator simply reversed the
plug, presenting fresh points and clean porcelain. Some were
'last gasp' attempts to keep failing companies alive, but
as the public gained knowledge through the 20's, these gadgets
and gimmicks disappeared.
Many companies failed during the 'Great Depression' and
very few survive today; much of the actual history has been lost in
the quiet of bankruptcy and corporate consolidation. Every now and
then an 'old timer' who worked for Splitdorf (remember the
green insulators?) or Benford will talk about 'the good old
days'and there are some members of the Spark Plug collectors of
America who specialize in brand name history. But for most of us,
spark plugs are simply a way to increase our enjoyment of early gas
engines or automobiles. We collect to display and talk about the
way things were. Spark plugs are a pleasant 'add-on' to
seek out while away on vacation .. . and we have something to look
for while Mama browzes through the pressed glass at the flea
As you complete the restoration of your latest gas engine, why
not consider an authentic spark plug? The originals rarely had ribs
on the insulators and almost never sported cadmium plating.
Don't be concerned with heat range; display engines generally
do little work. And don't even be concerned about proper reach
as long as the piston passes top dead center without interference.
If the insulator is sound (no cracks), the plug will probably run
just fine. You will need an appropriate disassembly wrench and a
little gasoline or solvent to periodically clean out soot and
Should restoration be required, beware of high speed wire
wheels. Some brand names were 'top' printed and not
protected by the glazing on the porcelain. The inks are usually
resistant to gasoline, but a wire wheel can cause damage. Also,
brass parts are subject to smearing or 'orange-peeling'; it
is better to disassemble a plug before using a wire wheel to remove
In disassembly, use a pair of box wrenches, one for the gland,
one for the body, to avoid buggering the plug. If necessary, soak
the gland in penetrating oil before applying much force. This might
seem like common sense to engine restorers, but metal parts were
often thin and subject to distortion.
A good rub with steel wool and oil is often restoration enough
for metal parts. If a wire wheel must be used for cleaning or
blending surface texture, use a fine wire wheel at low peripheral
speed. A four-inch wheel at 1725 RPM is more than adequate. Do your
best to clean carbon from the porcelain and don't worry about
discoloration near the electrodes. Reassemble with just enough
torque to get a good seal, set the gap from .020 to .025 to
accommodate a possibly weak spark, and you're ready to go!
Spark plugs rarely 'wear out'. Cleaning will generally
restore them to good operating condition and you should not fear
using them. Your engine will be more interesting ... and as the ad
says, you will be too!
For information about the Spark Plug Collectors of America,
write the author at: g Meadow Lane, North Caldwell, NJ 07109, or
SPCOA, P.O. Box 2229, Ann Arbor, MI 48103. All letters will be