You could start by NOT undercarbing your 440 like too many people on here seem to do. A holley 750 is nowhere near enough for that motor with that kind of cam....especially if it still has the same jetting it came with out of the box. And an edelbrock 800 will not be a step in the right direction either. Sure, they have good just off idle response in their accelerator shot, but they are lean as heck form there out becuase they do not hold any danged fuel.
You need a holley 850 double pumper for that motor that is properly jetted and fitted with squirters and eccelerator pump cams to compliment said jetting.
You will not recognize the motor in the world of difference in its runability and performance.
well a 750DP is a fine carb for a mild 440. What killed his 509 is probably lack of gear and stall. The thundr 800 is not as good as the 750DP. Or compression or all of the above. That said if you are going to buy a new carb the 850 would be better. As far as cam what gears are you running and what stall? That VooDoo is going to like at least a 2800 stall and some 3.91's to work well.
