I've added HEI to my 69 442 w/1974 455. I have trouble starting it which I attribute to not having a working choke just yet. Once the car is running and warm, it runs fine. I re-read some of the HEI conversion threads and they say I have a yellow and purple wire. Mine appear to be yellow and black to the distributor (I combined them at the dist). They also say I only would have 9 volts to the distributor and to run a separate wire from the IGN terminal in the fuse block. When I un-plug the connector at the distributor and turn the key to run, I get 12 volts not 9. Does it switch from 12 to 9 when the car is actually running? If I'm getting 12volts with the ignition set to run then why do I need an auxiliary power source?


Thanks,
Randy

 

Those are the wires to the starter.

The distributor has a yellow (from the starter) and a resistor wire, with a sort of braided covering.


Because you're checking the voltage with no load on the circuit.

Go out and start the car and check it with the motor running. The voltage will drop.

- Eric

 

I wouldn't pay too much attention to wire color (unless you're certain with a repro or original harness in good condition). Too many changes over the years can lead to strange or confusing wiring colors/problems.
The harness should send an ignition wire to the starter solenoid to activate the solenoid/starter when you turn the key to 'start' position. Once you let go of the key and it stays in the 'on' position, the solenoid and starter are deactivated.
I'm not sure on '71 but on the '69, a ballast resistor is used on the wire that runs from the solenoid to the cylindrical coil. This is intended to keep 9V at the coil rather than 12. With the HEI, you will not need this wire coming from the 'R' side of the solenoid.
Your HEI should only have 2 connection wires; one is for the 12V source (must have 12V with key at 'start' and 'on') and the other is a tach lead. The 12V side of the distributor should have 'BATT' or something similar molded into the plastic to indicate this is the power side. Everyone has a different suggestion on where to pull the 12V from but the cleanest is the one the Olds guys provided in the fuse box. There should be a blade terminal marked 'IGN'. If you put a meter on this terminal you'll see that it should have between 9 and 12V with the key in the 'start' position and 12V in the 'run' position (this assumes you have a healthy battery). The voltage drop while starting is due to the losses/drain on the system in the starting circuit.
All in all the HEI wiring and circuit is a lot cleaner than the original coil set up. I went through this several weeks ago and haven't had a problem once I sorted things out.

 

Yes. Should be purple, to the S terminal of the solenoid.


Yes.


No. The ballast resistor is between the ignition switch and the coil.

The yellow wire from the R terminal of the solenoid connects the coil directly to the battery, bypassing the ballast resistor, to provide full voltage to the coil while cranking (ie: while the solenoid is pulled in).


Maybe. If all is well, in a post-'67 or so car, you shouldn't need it, but, depending on the condition of your wiring harness and terminals (cumulative corrosion and resistance), you may benefit from leaving it in and taking the current right from the battery while cranking.

In an earlier car, the car will not start without this wire, as the ignition switch doesn't make contact with the START and RUN circuits at the same time.

- Eric

 

Thanks guys, I have to apologize for the detail I typically require to fully understand.