What should coil and ballast resistor voltage be?
I'm having an issue where the car doesn't want to fire when warm (fresh build/restoration) so I measured the coil and ballast resistor voltage when warm (engine not running). In the run position it was 4.8V/6.0V respectively which seems low. I had just tightened the neg wire on the coil which wasn't as tight as it should be and the car did fire so no idea yet whether this was the issue or not. All the engine bay wiring harnesses and battery are new as well as the Mancini distributor, orange box and resistor. Any thoughts on those voltages?
That voltage will VARY according to supply voltage, the ballast, the coil, and the temperature.
When you twist the key to "start" the entire "ignition run" (IGN1 terminal at the switch) GOES DEAD. The starting voltage comes from the ignition switch from the IGN2 contact, which is seperate from but works like the "start" contact. IE IGN2 is live only when cranking. THAT wire, normally brown, goest to the coil + sided of the ballast, and is supposed to supply battery voltage direct to the coil when cranking.
I've written hundreds of posts on these issues. VOLTAGE DROP in the various bulkhead connector terminals, specifically the big black and big red ammeter wire terminals, the terminals at the ammeter and the ammeter itself, the connector for the ignition switch and drop within the switch contacts, and drop through the bulkhead connector terminals for the IGN1 and IGN2 circuit.
"For now" your "run" coil voltage is fine
Put your meter on coil + to ground, Crank the engine USING THE KEY and read the meter while cranking. You "should" have same as cranking battery voltage, and should have a minimum of 10.5V
Now, the ECU still has to get power when cranking. HOW does that work? When cranking, and IGN2 is activated and powering the coil direct, IGN1 is disabled, so the ECU would not get power. BUT POWER ACTUALLY backfeeds through the ballast and to the ECU, so the ECU fires the car on REDUCED voltage.