I get up in the morning and my 76 280z starts right up, if I let it idle too long it will stall out. I will drive it for a little bit (under 5 minutes) and turn it off and when I try to start it up it wont start. The few times it does start it will idle at 500 rpm and with any pressure on the gas peddle lots of grey smoke comes puring out the back. But, if i let it sit for a while (7 hours today and yesterday) it will start up again no problem. Any one seen anything like this?

Did you try to jump-start it with another battery when it wont turn over? A friend of mine had a similar problem with his truck, and replacing the battery seemed to fix it.

Andrew