Brad - My guess would be that the engine you are looking at was either originally a fancy speed (they have been made with dual spark plugs for speed. Look at the modern Lion Head)
OR an airplane engine head. redundancy is nice to have in the air, and airplanes had two sets of magnetos. One electrical system goes out, switch over to the other and keep 'em flyin'
I also found this on a Harley website: Interesting Info:
Quote:
In 1917, Liberty Aircraft discovered that simply adding another spark plug to the opposite side of the combustion chamber and increasing the voltage at the plugs would cure detonation and increase power.
The same dual plugging solution was incorporated by Continental and Lycoming in the 1920s and 30s. Primarily used as a safety factor, it also reduced spark plug fouling and detonation and increased RPM..
For exactly the same reasons, your Harley motor can benefit from dual plugging. Dual plugging will “undo” the problems with its combustion chamber design and help your Harley run happily on unleaded gas.
Dual plugging alone of a stock motor will eliminate most detonation, stop plug fouling and hard starting, increase horsepower by five percent or more, increase gas mileage, double spark plug life, and lower emissions. Some tuners have reported six to eight percent increase in gas mileage.
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Quote:
Originally Posted by Brad in Germany
At Rétromobile in Paris, France last year I saw this rather interesting Model A head. It was made by the "Etablisement Veyet", Lyon, France.
What does the extra set of spark plugs do? I believe it might have been an attempt to squeeze a little more power out of the smaller AF engine that it is mounted on.
Fordially,
Brad |