This afternoon I took 2 of my cars for a ride before putting them away for the winter. The first was a '71 Cuda 340. It ran great for about 3 miles, started running rough, then died. After I got it (hauled) back to my yard I replaced the ballast resistor, then it would start..then die. The next car was my 69.5 Superbee. That car ran good, then when I rolled into my driveway, it died also. Same deal...it would start, then die and not run. I happen to try the Cuda after 1/2 hr, it started and ran good. I went back to the Bee and noticed the ballast resistor was hot, put on a used one, and after a few tries got it to run enough to get out back to my building..then it died again. Not until I put in an old ballast resistor, would it run enough, fairly rough, but I got it in the building. Any thoughts ?

ignition coil overheated perhaps?
happened to me on my truck once after i messed around with the ballast resistor.

First thing is that ballast resistors are suposed to be hot so doesn't give you much of a clue.

Pretty strange for two cars to have the same issue at the same time. I have to wonder if the problem isn't gas related and the ballast was just a fluke that gave the gas issue enough time to run a bit more. Have you bought gas for both at the same time recently? maybe you got some bad gas the last time. The next thought is about the opposite, the current swill they sell as gas doesn't have a very long shelf life anymore, is the gas in both cars more then 6 months old?

The ballast "resistor" is a wire wound resistor design the reduce the voltage to the coil, as it gets hotter the resistance goes up and reduces the voltage to the positive side of the coil even more.
Mopar engineers design the wiring to the ballast resistor to have a 12 volt bypass on the starter circuit to provide 12 volts to the coil in the start position only, bypassing the ballast resistor to help the motor start quicker and better, hot or cold

It was strange that both cars did that. I've been using race gas in all the cars for a few years now, since they don't get driven too often.

I have been using VP Vintage 98 on the cars I do not drive often. After some time I went to start my Cuda. It started and then stalled, I tried that a few times. Start and quit. I remove all the gas and put new gas in and then after a few times trying to start it finally stayed running. So bad gas was the problem. Even when VP said it lasts two years.
Bob

I always toss out resistors that failed in the past, but keep used older ones that were fine back then, if I happen to replace them with new ones while diagnosing other failing electrical components. I wonder if the older used ballast resistors have a "usefull" life expectancy. Every one I tried yesterday was one that I kept as a spare, not brand new......

The old recipe still holds, spark, fuel, and squeeze. I agree that it sounds like fuel. What's the gas smell and look like?

Race fuel, that's what I have been using for years....no pump gas.

With it being both cars I'd guess gas. All gas even race gas can go bad.

Yes, the race gas is a few years old, but it's strange that a different ballast resistor will allow them to run... I'll put in fresh race fuel after removing the gas in them ....next spring. Plus, other cars I have still run fine on the same race gas...strange...maybe it's just a matter of time before it effects them also. I'll try fresh fuel, and new resistors.

Thanks for all your input. I agree....Replace and add fresh fuel, and I think a new ballast resistor won't hurt , as possibly a better one that is on the cars gave a stronger spark and allowed it to run for a short while.

These are old cars and sometimes it's because of what crud or chemicals that have accumulated in the tanks over the years and got broken down over time. The longer the fuel is in the tank the worse it gets. The cars will start and run fine on what gas was in the carb but when they get the stale gas from the tank the problems start. If it was the ballast they would run fine after you replaced them.

Check the bulkhead connection on both cars. It’s a poor design that commonly fails on these cars as they age. The ignition power is fed though male and female spade fittings that corrode and get hot. Look for damage. Clean, and make sure they are making a tight connection.

That's another thing I was considering, and will check and clean the connections on both cars. Thanks !

My 69 Super Bee had that problem. When it would stall the first thing I did was unplug the bull head connector and plug it back in. It would start right up. I finally bypassed the connector and never had the problem again.

Points and condenser or electronic ignition? I can't remember what year points were replaced by electronic. I found that if a points dizzy is exposed to humidity, the points cam gets a light flash of rust and it become abrasive on the cam follower. As the engine runs, the cam follower wears away closing the points adjustment. Remember that little felt pad in the distributor? Its job was to keep a little lube and rust preventative on the cam. Just a thought and my
Copper

UPDATE
I installed new ballast resistors on both cars and had no problems while taking them both for a ride.......so far.