engine problems need help!!!!

[agross2011]

1968 mustang 351 windsor, cam specs are 496 intake 520 exhaust 290/300 duration
edelbrock performer rpm cam and high rise intake
holley 750 single pumper 4160 model
engine is running fine, but when i let off the throttle it loads up and is dumping tons of smoke out of the exhaust, all plugs are a gold color it only loads up when letting off the throttle, i am out of ideas i cannot figure out why the car is doing this somebody help

[6t9mach1]

What color is the smoke?

[agross2011]

smoke is black, its clearly smoke from getting too much gas

[joorloop]

Originally Posted by agross2011

smoke is black, its clearly smoke from getting too much gas

Timing issue??

[Le Singe Psycho]

Maybe a float isn't closing (or two).

[69Mach1_itch]

Letting off the throttle changes the vacuum state - from low to high. How is the distrubutor advance line run - from full port vacuum beneath the carb, or part port vacuum above the float bowls? What happens if you block off the advance and retime the engine?

[mjb1032]

Have the valve cover oil baffles been removed?

[agross2011]

the timing at idle with vacume advance unplugged was at about 10 degrees btdc and with the vacume hooked back up at 4000 rpm it shot at about 37 degrees, how could i block off the advance the timing needs to advance no matter what, it is a vacume advance distributor only not mechanical.
and the valve covers are in stock condition...why?