For What Its Worth

HEI Ignition wire upgrade on a 66 Nova.

The idea is similar for other years, but exact color callouts or plug-in locations in the firewall may be different!!!

On the point driven ignitions, regular running voltage for the coil was 6 volts.  This is so the points wouldn't fry in a few miles.   A resistor wire or ballast resister was used to drop the voltage.  With an HEI you do not need this, in fact you want to get rid of it.  There was also a 12v JUMP wire from the starter to boost spark only during starting.  HEIs don't need this either.

• Wire A 66 and 65 4 and 6 cylinders the resistor wire ran from the firewall to the starter and connected to the post where Wire B connected.
  
• Wire A 66 & 65 v8 from the firewall to the coil.
• Wire A is a resistor wire and provides reduced RUN voltage to the coil.

The resister wires were white/orange/purple and some may have an a cloth like feel to the cover.

• Wire B A black and pink wire ran from the starter to the coil also.   This post on the starter was energized when the solenoid engaged the starter. It provided a 12V to the coil over-riding the resistor wire while the starter was cranking.   On 4 and 6 cyl when the post was not energized, Wire B continued to carry the current for Wire A to the coil.

• The purple wire is from the firewall/key to the starter to engage the starter.  It is connected on the other side of the solenoid from Wire A and B.  LEAVE IT ALONE. This goes to the small S terminal on the starter solenoid.  The inboard one next to the block if there are two.  Solenoids for later model cars do not have the outboard wire connection.  It isn't needed with HEI ignitions.

When installing a HEI you remove the coil and replace the distributer.  The HEI will have a BAT hookup.

Here is what you do after you have the distributer in and are sure the cap clears etc.

1. Remove Wire B completely. It is no longer needed. You don't need the starter 12v jump with an HEI, it is already 12v.
2. Remove Wire A from the starter and trace it back to the firewall connector. (Or from the old coil to the firewall if an original V8 car) The outboard starter solenoid terminal will now be empty. It is no longer used.  If you have to replace the starter or solenoid, it will be easier not having to find the 2 terminal one.
   
3. Undo the firewall connector and Replace Wire A with a normal wire. Rewire the pin in the junction box to use a standard (red preferably) wire size, 12 gage everyone tells me.  Hey I have been doing cars so long I go by site not markings.  When I changed mine I carefully took the pin out of the connector. Small screwdriver or pin may be needed to push a spring clip keeper down so pin will come out. Then I carefully took the old resister wire out of the pin. Added and soldered the new wire in the pin for the HEI. Then re-assembled the firewall connector making sure the keeper snapped in and held it.  Don't loose or destroy that pin.
4. Check that the new wire has power in RUN and START key positions.  If for some reason it doesn't have power in START position, you may need to Keep wire B.  If it doesn't have power in RUN position, something is wrong.
   
5. Hook up new wire to the BAT post on the HEI.  Many auto part stores carry the Connector for the HEI BAT connection.  Now you have direct 12 Volt for the HEI.  It should be powered during start as well as run on the key. 

For reference here is a picture of where my wire was on the firewall connector.  67 and newer schematics show different locations.   This is a 66 and I don't guarantee yours will be the same even if a 66. 



Other links on HEI conversion

Oldengine.org

Happy Motoring, VHubbard.  July 2009

Last update Oct/2013

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