holley 1920 carb question

Yes. My first suggestion is convert to a late-model(77-79) Holley 1945. It's a better design with easily acquired parts and kits. You do need the matching electric choke unit for a 1945. There are those who love either but not both carbs, but in my experience the 1945 eliminates the headaches the 1920 causes.

Regarding the pair of 1920 carbs you are trying to make work:

The one that won't idle is probably dead. Those use a metering block and small passages in the carb that can corrode internally and according to most, you have to have the powers of Harry Potter to ever get them cleaned out again. I would move on from that one and forget it existed.

The second one that will actually idle sounds to me like it is not "venting" after it sits and heat soaks. In other words, the gas vapors that accumulate in the float bowl because of fuel perc have nowhere to go, so they hang around and get sucked into the intake when you try to start it, causing an overrich mixture until the engine pulls enough fresh air in.

If you are referring the '72 in your sig, there should be a metal or plastic nipple on the top front of the carb where the hose to the charcoal canister connects. Adjacent to that is a lever that acts on a small valve that permits fuel vapor to flow to the charcoal canister at closed throttle but not otherwise.

You can't plug that hose up. That'll cause the situation I just described. If you still have the canister, make sure it's connected properly. If no canister, then just run a length of line from the carb to a spot where the excess vapor and possible miniscule traces of fuel can safely exit.

The reason I went into this long sermon is that way back when, I had a friend with a '71 Demon slant car. In that year, cars with Federal emissions routed the carb bowl vent line into a port on the fuel pump because they didn't have charcoal canisters yet on those cars. It worked terrible and his car spun and spun like you describe on each and every hot start.

It also goes without saying that if the bowl vent isn't your issue then check your float level and also make certain the choke plate is totally open.

Lastly, I haven't had a Mopar that started quickly when hot since the gas turned into the ethanol junk. It just vaporizes too easily and causes problems.