I need a quick brainstorming session here:
Customer's car: 1970 cutlass. 350.

In for a complete tuneup because it cranks but doesn't start.

So far I have put in the new coil, new points, new condenser, new battery, plugs, wires, cap and rotor.

This thing cranks and doesn't start. I ran a new yellow wire from the R terminal of the solenoid to the + side of the coil. Reads 11 volts. But when cranking, there's nothing. Coil is not generating a spark.

Purple wire from the S terminal into the firewall is in good condition as far as I can see it before it disappears into the harness.

 

Check + side of coil with key on...should be voltage there thru resistor wire. Purple wire on solenoid runs from key start position thru neutral safety. If this was the problem starter would not crank. Smaller yellow wire on solenoid provides 12V to coil while cranking. Points must open and close for spark. With key on you can manually open and close points and should have spark from coil to ground.

 

So you get voltage with the key in the RUN position but not the START position? Could be wiring or ignition switch. Temporarily run a fused wire with a toggle switch directly from the battery to the coil. If the engine starts, you're isolated the problem to the purple wire or the ignition switch.

Also, you have verified that the timing chain hasn't jumped, haven't you?

 

Yellow wire reads 11.4 volts at the coil, but when cranking, voltage drops to zero. Ballast resistor and associated fuse had good continuity. Point gap is
.020" and closes at the peak of the distributor cam. I haven't torn it apart to look at the timing chain marks yet. Hoping not to

 

Take a #12 wire direct from the battery to the positive side of the coil and see if it starts. Do no leave it running if it starts this is just a test. If it does start then your resistor.

Could be that the starter soleniod is bad (not closing the contacts on the S tab