Low Voltage to the coil

I run a Blaster 2 with resistor supplied with Blaster 2, orange box spark control on my 67, and it runs and starts very well.

I suspect a voltage drop in the ignition circuit as mentioned above often caused by poor connections in bulkhead connector, and ignition switch. Other reasons for low voltage at coil can be caused by electric choke being feed from ignition side of ballast resistor, and poor grounding of spark controller, voltage regulator, and alternator cases.

A ground loop picking up the various cases via a conductor attached by one of each device’s mounting screws leading back to negative battery terminal will provide proper ground, and eliminate voltage drop on the ground side of ignition circuit.

Best way to eliminate resistance at bulkhead connections is to remove and replace the brass connections. This is tedious one wire at a time work, but brings the bulkhead connector back to like new condition. Second best way to eliminate bulkhead resistance is to just clean, and tighten each existing brass connection.

Also clean and remake battery terminal connections, and ground attachment points at block, fire wall, and while you are at it headlight ground to sheet metal connections.

If equipped, powering electric choke from under hood source (battery alternator starter relay) with a relay triggered from ignition circuit will eliminate almost all voltage drop caused by the choke at the coil.

I had my choke directly powered from ignition circuit; it caused a one volt drop at coil. A relay system controlling choke corrected the voltage drop.