Late last summer my car suddenly became difficult to start when the engine was cold. Normally it would fire right off and run great even after sitting a week or so.

Now when cold, after sitting overnight, I need to crank it for about 10-15 seconds, then it will fire, run rough for 30 seconds or so then smooth out.

I have 2 different carbs and it acts the same with either. Both are Edelbrocks (I've had good luck with them). I'm not sure how to tell if there is fuel in the bowls after sitting overnight. Both electric choke style, chokes seem to work fine.

GM HEI, newer plugs and wires, Pontiac 400.

I'm stumped, but then I am not very good with this sort of thing. Thanks for any suggestions anyone has.