It looks to me that the timer makes contact form 15 to 20 degrees, depending on the timer used. If this duration was shorter wouldn't it be a easier on the points and coils when on battery? Doesn't the combustion need only a flash of spark to set it off? When running on mag is there only a single flash of spark? I've wondered this for years. With all respect Bob Shirley, Atlanta TX.
Running on the T magneto things function much differently. Only on battery do you get what you are describing. And Ford intended it to run on mag all the time
The timer gives the cylinder selection to the ignition system. It is a small part of the equation. Keep your Ford roller timer clean and lubricated, it will last a lifetime. As mentioned, a battery is not the intended source of ignition power. Your car will run infinitely better on MAG.
Beware of many reproduction roller timers, they are inferior to originals.
Magneto gives several flashes of spark throughout compression and expansion duration so if the mixture does not ignite the first time it will later.