<VV> "Points" to ponder - Pertronix Issues

Padgett pp2 at 6007.us
Fri Oct 28 08:49:46 EDT 2005

>There  are several reasons that all of the car manufacturers changed  from
>point actuated ignitions to electronic based distributors, then  eventually
>distributorless electronic ignition systems. First was  the advent of Smog
>regulations. ..

Actually electronic (aka transistor aka breakerless) ignitions go back to 
the period prior to the GM racing ban in 1963. The Delcotronic ignition 
intended for introduction for the 1962 model year was a great improvement 
over points. That there was a problem had been acknowledged  much earlier 
and led to the rise of the Mallory Magneto ignition and  by the late 1950's 
dual point distributors from Delco-Remy were common on high-performance 

The Decotronic consisted of three major elements, an amplifier that had to 
be kept cool so was usually mounted in the wheel-well, a magnetic impulse 
unit replacing the points in an otherwise conventional distributor, and a 
special high-voltage coil. Plug gaps were also commonly opened up .015-.020".

The system placed the amplifier between the 12v source and the positive 
terminal of the coil with the negative side of the coil connected to 
ground. This meant that a conventional passive tachometer that was 
connected to the negative side of the coil would no longer work and a 
transistor "boost" circuit was developed so that the tachometer could be 
connected to the positive side. If you look at the schematic it can be seen 
that the transistor circuit is merely a front end on a conventional passive 

The Delcotronic was in production until 1966 when it was replaced briefly 
by a Capacitive Discharge unit which led the way to the first HEIs in 1971. 
These early units had a much smaller diameter (drat, it is hard to tell 
this story without illustrations) than the 1973 HEIs which followed as it 
was found that 60,000 volts would arc over considerable distanced. These 
lasted until 1986 when the first Distributorless Ignition Systems (DIS) 
were introduced though the full transition took several years.

So it was racing and high performance that led to the development 
of  transistor ignitions, not smog. If you get a chance to see any NASCAR 
footage of the interior of GM race cars in the 60's and 70's, many had a 
pair of Delcotronic amplifiers (if one failed, ignition could be switched 
to the other) on the passenger side of the dash.


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