I have a newley assembled 396. I got this thing in a big trade, and dont know much about it. Here is what i know. It is 10.5:1 compression, a lunati Bracket master 2 294 cam, dual quads on a tunnel ram, a complete msd ignition. I know the heads are in ok, but not great shape. the problem is i cannot seem to get this thing tunned right. It really runs terrible, and back fires through the carbs constantly when accelerating. I would like any suggestions as how to cure this. I dont want to drag race this thing, i just want it to run respectable. the carbs are brand new Holley 450 cfm right out of the box. I have tried to use a timing light on it, but the timing is too eratic. Once it is running at idle, it sounds good and stays cool. My goal with this thing is to have some drivability with it. Any suggestions would be appriciated as i am guite new with setting up dual quads, and big blocks in general.