I have a used Edelbrock Performer, 600 cfm, 1406 carb. It’s always been floodish but I had it on a worn out engine. I rebuilt the engine. I put vortec heads on it and performer rpm intake. The cam is 447 intake and exhaust 454 lift 212 duration and 218 duration exhaust. It starts right up but It was still floodish. Falls on it face when I punch it to the floor on the rebuild engine. So I had a carb guy put a carb rebuild kit in it. He found Black tar like stuff all the way through the carb. Now I have it back on the engine. It does not fall on its face like it was doing. But know if I shut if off for like 20-30 min or longer and start it up. It cranks several times and then finally starts but it is flooded and a lot of black smoke comes out of the exhaust. Then it finally cleans up. What would cause this problem? Thanks