Purge line 1920 carb

If it has a canister it's a 1972 or later.

On my '73, there is a large line that runs from the connection on the canister marked BOWL to the bowl vent tube at the top of the carb. It's at the front, points to the passenger side and has a bend toward the rear in it.

If your carb doesn't have that then it's an older carb or a truck version that did not use any type of vapor recovery system.In that case there's no place to hook it up, as those carbs simply vented to the atmosphere.

The correct carb also has a medium-size connection at the bottom, valve-cover side that is the purge port connection. The canister has a matching port that is labeled PURGE.

IF your car is a '72, there are some changes to that arrangement. That year used a separate purge valve. There's a thread somewhere that discusses that. Might be on slantsixdotorg.

IF your car is a 71, it won't have a canister unless somebody added it, and who would. The carb vent hooked to a port on the TOP of the fuel pump in the misguided idea that the carb vapors could be sucked back in and reclaimed somehow. There's more to it than that, but that's the gist of it. My friend had a '71 with that arrangement and it always was a hard hot starter because the carb vapors had no place to go.