Coil too hot for points?

John T

First, that so called super coil or those high voltage coils STILL FIRE AT THE SAME VOLTAGE the old stock coil does given the same plug gap and combustion conditions (fuel type and compression). The firing voltage is a function of the plug gap and the medium in which it fires. The high voltage super coils are merely "capable of" ramping up to those higher voltages when and if necessary which is usually accomplished by running wider plug gaps and/or under high compressions and exotic fuels.

That being said, Im thinking like my buddy Buick in that the super coil may well be lower impedance (Then a stock coil of approx 3 ohms if a 12 volt or 1.5 ohms if a 6 volt) and drawing more current then the points and condensor were designed to handle. Overcurrent and its resultant heat are enemies of both the points and condensor. A ballpark figure for points and condensor switching is somewhere around 4 amps max.

To get the benefits available from a super coil, one usually uses an electronic switch (like the Pertronix) which can handle the higher coil current plus is a faster more positive switch with less ringing. They usually run a wider plug gap and end up with a fatter wider hotter spark to better ingite the fuel.

I dont see much if any benefit from the use of a super coil if youre still using mechanical ignition points and running the same plug gap, it still fires at the same voltage the stock coil would have. Plus, if its of lower impedance and the points and condensor are switching much higher then 4 amps, they are both gonna wear out soon. However, the super coil may be more efficient (less heat losses) to gain some advantages all else being equal.

Bottom line, if youre still using points, you should either run the stock coil or add the necessary external current limiting ballast resistance to achieve a total of around 3 ohms total (ballast plus coil) in the primary coil circuit. i.e. if the coil is 1.5 ohms you would need to add an external ballast of 1.5 ohms around 25 watts.

Clear as mud?????//

John T Nordhoff in Indiana, retired electrical engineer

Yes, I lead a double life.

b&d

thanks Dave

In cases of a 12 volt system with a hot coil and an electronic switch, theres usually no ballast at all required, but to be safe the current rating of the elec switch has to be rated to handle whatever current the coil draws and that has to be a question for the elec switch manufacturer (like Pertronix etc). I believe they make a couple different current rated electronic switches, one for one family of coils and a higher current rated switch for their super high energy coils?? In most cases, theres no ballast provided the switch is matched to their recommended coil.

I guess Im saying you better check with Pertronix to be safe so the switch can handle whatever current the coil draws.

Sorry I cant provide any exact answer, but theres too darn many unknown variables.

John T