carb/idle problem please help

[chevythunder]

i have a 74 K20 with a newer 350. after letting it sit for a week i started it up the other night and it wouldnt idle and skipped and sputtered when i drove it. so today i took the carb off (edelbrock 750) and took it all apart sprayed it out with carb cleaner and air. i put it back on  and it idled and drove good. but when i came home and parked it in my driveway all of a sudden it started idling lower and lower to the point where it was about to die so i revved it up a little and black smoke came out of the tailpipes and it idled good for a half minute then did it all over again. i took it for another ride and it runs great when your on it but when i let off the gas and slow down or have it sitting in park its like it starts loading up and idles down and dies. i am guessing by the black smoke its running rich. anyone have any ideas? all help is appriciated.

[chevythunder]

bump

[Blazin]

Sounds like its loading up to me. Is the choke sticking part way closed? Might be time for a rebuild, and not one in a can. Or put a real carb on it, a Quadrajet.

[VileZambonie]

Pull the airhorn off and check your float level and float drop. Remove the needles and seat and clean out the inlet good. While you have it out run a piece of mig wire through the jets, there are 5 on your carb.