I just had my 350 sbc rebuilt and put in my car. It was a total rebuild including the heads. On the first start up it had hardly any smoke and ran fine. The only problem is when I give it hard acceleration it starts to smoke really bad, and wont stop. After letting it sit for about a day i went and started it and it hardly smoked so i took it for a drive and it started doing the same thing again! What could it be?