Jim, Here is a link to a Healey owner who has posted information from
a Champion manual about polarity and spark plugs.
Mike (not an engineer or a mechanic)
"Spark plugs are sensitive to polarity and they will not function as
efficiently it the secondary coil voltage is of the wrong polarity.
The reason for this sensitivity is as follows. The centre electrode has
a higher temperature, normally, than the ground electrode so that more
electrons will be released from the hotter metal surface of the centre
electrode than from the ground electrode.
If the centre electrode polarity is more negative than the ground
electrode (which is connected to chassis) then the earth electrode will
attract electrons from the centre electrode; but if the coil secondary
voltage polarity is reversed, the voltage needed to cause electrons to
pass from the earth to the centre electrode (i.e. to make the gap
conductive) is increased."
> I still can't come up with a single tangible negative
> impact from leaving the coil wired "backwards", other
> than confusion in later electrical diagnosis work.
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