Tuning (PLEASE HELP!)

[King Big Ben]

Ya it's me again...anyway I've had this 650 speed demon carb in my car (69 coupe w/ 351w, edelbrock intake, and what I think is a stock cam, and stock exhaust manifolds w/ aftermarket h-pipe exhaust) for a while now and it still needs tuning. It runs rich and you have to rev it up slowly or else it will backfire (which i thought was a symtom of it running lean). I figured i need to adjust my timing, so i bought some timing tape but I'm not sure how to put it on (What's a TDC mark?). I did put new spark plugs in which actually made it run perfectly for about 10 seconds. It didn't hesitate or backfire and it sounded perfect...and then it got back to the way it was before. I took out one of the plugs out and it was clean except for around the edge it was a little...i guess you would call it sooty but where the spark was was perfectly clean. Please help me with this...I dont like how my car sits at home all week because i can't tune it and none of my friends know how to tune it and the people who actually can help me are always busy.

Thanx in advance,
Ben