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Our previous articles have touched on various parts of
the Model T ignition system. We've talked about the timer, magneto and
coils. Let's finish up with a final, but vital, part of the ignition
and talk about the choices of spark plugs that are now available for the T.
While some of us may not think so when watching the steam issue from the
radiator, the Model T engine has a relatively cool combustion that's typical
of most of the low compression engines of the early 1900's. This means
we will need a fairly hot plug if we want to avoid fouling and get the best
efficiency.
Plug temperatures were controlled by the length of the porcelain insulator
that was exposed around the electrode inside the firing chamber. A
long exposed area would transfer less heat through the plug body to the head
and would heat up more.
All Model T's came from the factory with Champion "X" plugs.
This was a very good spark plug for the T engine with a hot heat range that
was nearly ideal. Champion still makes these plugs but the price has
risen from seventy five cents to between twenty-five and thirty dollars a
plug! Of course you'll use this plug if you are building a show car
but for those of us who don't have show cars and want dependable smooth
engine operation there are other plugs available that won't require a trip
to the bank for a loan.
There are several choices available from all of the model T suppliers.
I've tried all of them except the Autolite so let's look at the various
brands and what they cost.
The lowest priced plug is the Autolite which not all suppliers even list.
Langs does include it in their catalog. At the time I am writing this,
the price listed is $3.40. As I mentioned, I have not tried this plug
and would like to hear from anyone who has used it and how they liked it.
At very close to the same price, is the Ford Motorcraft 11 plug at $3.50.
Now, you would think that Ford would know how to make a plug for their own
car but I have never been able to get this plug to work well! Looking
at the plug, I am really puzzled by this. It's obviously a hot plug
and I can see no reason why it shouldn't do a good job but I've tried it in
several cars and with several plug gaps and have always ended up removing
them after a few miles. They ran ok at cruising speeds but I was never
satisfied with the idle.
Next in price is my favorite plug for a driving T! The Champion 25
plug. These plugs cost more but, in my opinion, they are worth
the difference. They currently sell for slightly less than $9.00 each.
They are a hot plug and provide smooth cruising and a very nice slow idle
without a miss!
The most expensive plug is the Champion X plug. This plug works as
well as the Champion 25 but at a much higher cost of $25 per plug.
This plug has a tendency to widen its gap more quickly than any of the
others because of the smaller diameter of the electrodes so you should check
the gap more often with the X plug but they do run well. Be careful
when gapping NOT to bend the center electrode and crack the porcelain!
.
The final option is the 14mm adapters which allow us to use modern plugs.
I'm less than enthused about these for several reasons. They don't
look original, they provide more chances for compression leaks. Of
course, they do let you use the seventy five cent plugs again!
Before leaving the subject of sparkplugs lets mention the correct gap.
Ford recommended a very narrow 25/1000's for the early T's. He later
increased the gap for T's to 30/1000. I usually use 35/1000 and really
can't see much difference. I would NOT exceed 35 because of the
additional strain on the secondary of the coils.
See you down the road…
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