Positive Ground and Coils


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By petew - 15 Years Ago
  I have a 55 Tbird with it's original positive ground 6 volt system. It currently has a pertronix system on it and I just discovered that the coil Pertronix recommended ( and which is currently installed in the car ) is in fact a 12 volt coil. This raises the following questions.

1. What are the problems that can come from running a 12 volt coil in a 6 volt car?

2. And what is the proper way to wire the coil on the original points ignition with pos ground ?Does the battery lead ( 6volt switched ) go to the neg side of the coil with the points lead going to the pos side ?

The car runs well with the Pertronics but has a rougher hot idle then it had with the points ignition. Starts poorly cold but well hot.

Pete 

By rick55 - 15 Years Ago
If you are running a 12Volt coil -ie marked 12V - you are only getting half the output from the coil that it is capable of.

If you are running a resistor type 12V coil, which is really an 8Volt coil there probably isn't any real difference in a 6 Volt coil with a fully charged battery (usually about 7Volts). 12 Volts is only applied to this coil whilst starting. This would explain why the car starts better hot than cold - as the battery is freshly charged and may also affect idle quality.

This is part of the reason why cars moved from 6 volt to 12 volt.

If you are running a 12 Volt Pertronix system in a 6 Volt setup with positive ground I am surpised it works at all, though if it does I would expect it to be hard to start.

There is a Pertronix setup for 6Volt positive ground. The Pertronix system is merely an electronic switch for the points and the standard coil should work properly in this system.

Check out these instructions.

http://pertronix.com/support/manuals/pdf/ignitor6vpos.pdf

Regards
By petew - 15 Years Ago
Yes, this is a positive ground system and they (Pertronics) like you to use one of their coils and their ignition wires as well as the combined resistance is most compatible to the actual Pertronics ignitor.

The coil is the unit they specificied for the ignitor. I am upgrading to a 465cfm Holley to replace the teapot and will be using a 57 Tbird distributor as the 55 distributor is a Loadomatic that goes with the teapot . As such I am going to dump the Pertronics and go back to points with a new 6 volt coil.

By DANIEL TINDER - 15 Years Ago
Pete,



Must be a new development with Pertronix (?). When I had the 6V/pos. grd. version a few years back, only the Pertronix II version (not available then in 6V) was recommended for use with their coil. The power drain of my OD system caused missing at high RPM with headlights on, so I went back to points.