Changed the ignition switch on the column. PITA unless you are two feet tall with really long skinny fingers. That being said, did not help my problem. I am getting a spark after I let go of the key switch, not while cranking ? However to make it more complicated once the car warms up I can most of the time start it normally. I have a mallory spark booster which has a self test that checks out., as well a hei distributor that is OK. What else could be causing the pink ( from ign. switch ) wire to drop below 12 volts while cranking ??

The actual key cylinder is purely a mechanical link from the key to the switch. That's not gonna effect the electrical issue.
Have you tried running a 12v, key on wire to the HEI(Batt), to see if that will solve the problem?

Do you mean just attach a 12 volt power source to the pink wire coming from the switch harness?

Actually, I was thinking of running directly to the "Batt" terminal on the distributor cap, and disconnecting the wire that is there now. Just to see if the thing would start properly when the problem raises it's ugly head.

I'm starting to think there is a problem with the Mallory system, regardless of the self diagnostics it may have.

You have to have a full 12v at the dist/coil for it to start. I'm still kinda in the dark as far as how your Mallory system is connected, so, anything I suggest is going on how an original HEI system works.

There may be something that is actually drawing too much juice from the "crank" circuit, and that is what is causing the voltage to go down....Adams' Apple2007-12-04 19:46:35

It is wierd, the pink wire only shows 7.0 volts when I am cranking. I thought it might be the mallory setup, but it seems like the problem starts out of the switch. I think I might disconnect the mallory and see if that rectifies the problem first. My back is killing me from screwin with that switch anyway.

Sounds like the switch down on the column is wearing out and or is dirty. You can spray electric contact cleaner in it and turn the key on and off (disconnect battery) then if you can put some dielectric grease inside it. Alot easier to replace it and you have a new one with lots of life left.