1970 Ford Mustang, Windsor 302 V8, C4 Automatic Transmission, Holley 600 Carburetor
I'm going to take a wild guess and assume that they could be for heater hoses, although that wouldn't make much sense......
This is correct, and virtually quotes the Manual.Ford gave it a fancy name, something like Distributor Vacuum Control Valve.
Below a certain temperature it directs "ported" vacuum to the distributor vacuum advance canister. With ported vacuum there is no vacuum with the engine at idle and therefore no vacuum advance.
If the coolant reaches a certain higher temperature the DVCV changes and directs "manifold" vacuum to the distributor vacuum advance canister. Since there is manifold vacuum with the engine idling the distributor vacuum advance canister is activated and the advanced timing causes the engine rpm to increase which causes the fan to spin faster and bring the coolant temperature back down.
Before the DVCV was invented Ford/Autolite put hot idle compensators (Klutch mentioned it) on the carb to increase the rpm when the carb got hot.