Rough idle at start.

[brown7373]

I continue to have a ridiculous idle on a cold start. I live in south Florida, so I don't mean freezing temps, just sitting over night. It is a crate 350 engine 350/290 4 bbl Q-jet. It seems like only running on 1/2 the cylinders. But If I put it in gear it idles perfectly. Once it gets a little heat in the engine it runs fine. Carb has been rebuilt and it and the choke function as designed. Oh, and it is lucky to get 8 mpg. The original engine got 11-12 mpg. I have heard I need a different torque convertor, but that would have nothing to do with the idle. And once started, and warmed just a tad, it will continue to run fine all day long.