MTFCA Forum

What Edison spark plug (number) works in a Model T? I have heard that number 14 is the correct number. Are there other numbers that work? Jim Patrick

So, #13 and 14 are for use on a Model T. What is the advantage of the double electrode on the #13? The Edison #14 looks like the Champions I have. Which one of the Edison’s works the best? #13 or #14? Thank you. Jim Patrick

I use the #13 Edison plug just because it is large...1 1/8 inch wrench...Edison plugs in a Ford kind of goes together...Robert

I have a set of Edison 14s in my 1924 cut off touring, I like them. I installed them in 2013 and haven't touched them or looked at them since.

I have three Edison 13s, but I haven't run them yet, so I can't compare them to the 14s.. If I can find a fourth one I might try them in my 1912 Flanders 20 at some point. Right now the Flanders has Bethlehem "five point" plugs in it, pics are in my OT Flanders thread. The Flanders isn't running right now, so I can't comment on how they run except that the one I pulled out had good color on it.

If someone has more of the Bethlehem plugs in good condition like the ones shown in my Flanders thread, I would consider trading my Edison 13s for them.

Almost 10 years ago, George Mills and I installed a set of NOS Edison number 14 spark plugs in the 1922 touring car at the Glenmont estate of Edison's in West Orange New Jersey. Gap was checked at 0.025", and and runs great on battery and magneto. If there ever is another Saint Patrick's parade in West Orange we will be called to check everything over.

As Robert said, T’s and Edison just go together. It would be interesting to know just how much input Edison had when The Model T was still on the drawing board. Since Ford worked for Edison as and engineer at the “Edison Illuminating Company” and later, became such good friends, I can imagine in 1907-08, Edison and Ford mulling over the Model T (and perhaps earlier Ford cars) blueprints, while Ford peppered him with questions, in an effort to mine Edison’s brain for his genius. I’ll bet Edison’s influence is all over the magneto, generator, spark coils and electrical system in general. Jim Patrick

From my knowledge of Edison, I’d say little to none, Jim. Edison famously said he would never own an automobile with ball bearings. He was a fan and owner of Grout steam cars. Also, of course , very interested in electric automobiles. I don’t think Ford bought the home next door to Edison in ft Myers until the mid to later teens. Edison accepted a later gift of a maintained model T touring for his winter home, Seminole Lodge, which Ford milked for 100x more than it ever cost him. Edison distanced himself from Henry during the peace ship fiasco in the late teens. Henry visited Florida very little, usually just around Edison’s birthday celebration in Florida. Henry would famously sneak off the train on the stop before ft Myers and walk the rest of the way, to avoid reporters. Edison was Fords idol, not the other way around, for sure. Of course, IMHO

Ford had great respect for Edison

Does anyone have a conversion chart for Edison plugs? I have several boxes of new plugs of various sizes and don't know their application.

This may help :

https://www.bing.com/images/search?q=ed ... BasicHover.

The multiple electrode thing is basically a bit of snake oil that has been around for a very long time. Many very early spark plugs (think before 1901) used a multiple point or ring type arrangement before experimenters went to the more common newer design. The ring or chamber style early plugs fouled badly, and were not reliable. The more open electrode designs worked better (stayed cleaner). However, within only a very few years, people began marketing multiple electrode designs. The theories sounded good. Two sparks had to be better and hotter than one, right? Reality however, doesn't work that way. MOST of the time, only one such electrode actually fires a spark. Once the voltage is ready, and the points fire, the voltage will fire the path of least resistance. One electrode or the other will foul a tiny amount, and the other one will fire alone for some time until circumstances change. Once in awhile, the path resistance will balance, and the two electrodes will alternate! I actually saw a high speed camera film of this many years ago in relation to electronic pathway studies. Fascinating to watch. The camera actually filmed the inside of a running engine cylinder, aimed at the spark plug electrodes.
True dual ignition can add somewhat to engine power. It works as long as the sparking points are separated, and the voltage sources are also separated. Timing between the two separate systems is critical. In the real world, single voltage source dual electrode plugs just doesn't add much. It MIGHT help a bit against fouling issues under SOME circumstances. And it could maybe help a bit if/when the electrode is badly burned or otherwise damaged. Otherwise, pointless.

In spite of that, they have been marketed over and over again for more than a hundred years now. I have a few Edison 13s (don't want to sell them), and have seen several others offered in the 1910s and 1920s. I have also seen ads for them from the '30s, and know the idea was quite popular during the 1950s. I have seen a few over the years since.
Last July, I had to do a tune-up on my 1998 Toyota in order to pass the regular Califunny smog inspection. Somewhat to my surprise (not really surprised?), one of the options I was offered for spark plugs, was that same old dual ground electrode.