i hope you guys can understand what i'm trying to say here, but here it goes. when cold my '80 f-150 400 would idle rough and die but when warm it was fine. there is also a constant flow, sounds like a vacuum leak near the brake pedal in the cab that once i step on the brake it goes away. i checked timing, good, then tuned up the carb a little bumping the idle up and mixture up. then it ran like a top. for some reason today on the way home it continually died whenever i came to a stop. after a couple of times i would put it in neutral but it would still die. one time the light was red and i was slowing down then it changed to green and when i went to speed up it knocked a little and backfired then died. after that when i was going up a hill it started to knock violently and the engine would cut away but didn't die. it did this about five times and then finally smoothed out. once i got home and got it parked it turned it off and started it up again. it was idling fine but once i shifted it into drive it instantly died. what the heck it my problem here? any input, advise, or solutions would be much appreciated. while i wait to see what advise you have for me i'm going to check all my plugs, valves, vaccuums, dwell angle, etc.
thanks for you time.

 

also, when i was looking at the carb, when it died a cloud of gas shot up from the carb. also when in idle, the exhaust is chugging from the tail pipe, da-da-da-da-da-da-da, like that
80,000 mile, stock
thanks

 

You might wanna try a carb rebuild kit, and if that doesn't help check the timing chain.

Hope this helps!!!
John