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360 stumble

hi, I have a 1976 f-250 ranger. it has a all stock engine (rebuilt in the 90’s so it’s not all worn out from 30+ years of work). When I have it operating temp, and let it idle down for lets say, as long as it takes to sit at a red light (a min, or so) when I go to step on it to take off it stumbles until you get up to about 5 mph or so. Here’s the catch though, if I pop it into nutral and rew it up a few times right before I go to take off it does not stumble when I step on it. Any idea how to fix this? thanks.

I am not a real carb man, but I suspect your problem is at the carburetor.

yes, I think that might be it, it has had three carbs on it since the rebuild. I just need to know how to fix it.

Possibly the fuel pump can’t provide enough fuel to the carb at idle, then when you take off you are lacking fuel to the engine. I suppose you could narrow this down by seeing how it reacts at a stop sign, where there isnt enough time for the fuel bowl in the carb to run dry.