[Farmall] Oliver Cletrac HG Question

[soffiler at myeastern.com]

From: Mike Sloane <mikesloane at verizon.net>

> 2. While the tractor will run with no other changes than
> above, it will  not run well until you reverse the coil
> connections. Automotive coils  are "auto transformers"
> with both high and low voltage common on one  side. It is
> my understanding that the running them reversed will
> degrade  spark voltage significantly. Fortunately, it
> takes only a few seconds to  reverse the wiring on a coil
> - make sure that the wire connected to the  distributor
> goes to the terminal marked the same as your ground (if
> you  battery is negative ground, connect that wire to the
> terminal marked  with a "-" and the wire from the switch
> to the "+" terminal).

Mike is correct.  The spark across a plug gap is actually a
flow of electrons - a tiny zap of lightning.  Electrons
prefer to jump away from an object shaped like a point; this
is the center electrode.  So the coil polarity is set up to
force the center electrode negative with respect to the
ground electrode.  If a tractor is changed from postive
ground to negative ground, without changing the coil, the
spark plug is being asked to work "backward".  Which does
work, but not as well.

(A couple additional comments - (1) if anyone has seen the
tip of a modern Platinum spark plug, you'll know it is very
very narrow, much more pointy than a good old everyday
sparkplug.  More pointy is better as described above.  The
platinum resists erosion better, so you can get away with it
being smaller.  (2)  You find "distributorless" ignitions on
modern automobiles that often use one coil to fire two plugs
simulaneously.  One of the sparks will be "backward" which
goes against the principles described above.  However it
works fine simply because modern ignition systems have
vastly more power than the systems used on old tractors.)

Steve O.