I have a 1975 280 6 cyl. four barrow carb. It starts first try but when warms up and chock gos off it dies fast. if you give it gas it will stay running will not idle!! I have went through carb 4 times; nothing in idle passages, jets clean, power to injectors and they click when I turn key on,no vacuum leeks, good spark, fuel filter good , new fuel pump. Only thing I dont know about and haven't checked is float level ( it should be ok) but if not would it effect the idle_after chock gos off??
DONT understand

My old 280 had a vacuum operated idle control system (the big metal vacuum element on the left front side of the carb). You should adjust the idle with the screw below this element. If you have the correct idle rev adjust the length of screw operated by the element. With the engine on normal temperature take the vacuum line off, adjust the screw of the vacuum element until the engine rev is 1600rpm. With the engine running you should see the vacuum adjuster move, it is designed to catch the linkage before the engine stalls.
The solex carb is very complicated, lots of things can go wrong. The idle system is separated from the main system, with separate air channels and nozzles. The electric things on the front turn on the idle system