For What Its Worth
HEI Ignition wire upgrade on a 66
The idea is similar for other years, but
exact color callouts or plug-in locations in the firewall may be
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.
The resister wires were
white/orange/purple and some may have an a cloth like feel to the cover.
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.
- 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
- 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
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
Here is what you do after you have the distributer in and are sure the
cap clears etc.
- Remove Wire B completely. It is no longer
needed. You don't need the starter 12v jump with an HEI, it is already
- 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.
- 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.
- 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.
- 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
VHubbard. July 2009
Last update Oct/2013
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