Thanks to all who ventured opinions on my query about old coils marked CB
and SW and their suitability for negative ground cars.
The consensus was that switching polarity would affect spark intensity. John
Seim suggested looking at a plug and noting whether the spark jumped from
the center pole to the side or vice-versa, then wiring the coil so that the
former condition existed. Here's the result of my testing ....
The car is a TD special wired negative ground, the coil a Lucas Sport Coil
dated 1966. With one lead connected to a new plug grounded against the
block, wiring the coil either way made no difference; the spark jumped from
the center pole to the side (though both sparks looked rather anemic). I
then tried holding the coil wire close to the block and saw a nice fat blue
spark which could jump 7/8" - once again, with no visible difference whether
the CB or the SW was wired from the coil to the distributor.
So, whatever the theory, it appears switching polarity on the car and using
an old coil doesn't really make much difference, if any!
Lawrie
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