full UDS coal basket = heavy white smoke

i have a typical 55gal UDS with a 13inx12in round coal basket. round metal grate on the bottom and expando on the sides, elevated 3-4inches. 3-1in inlets and 2in bung on a flat top lid. i burn lump, RO or Malic's, with hardwood chunks.

I typically fill the basket about 1/2 way with lump and hardwoods mixed through out. i use a homemade charcoal chimney made from a large coffee. once i have a full can of coals, i'll dump on top and let them sit for no more than 5min and place the basket in the UDS, close the lid, adjust my intakes to my typical 250F settings and i typically get stable temps and thin blue smoke in 20min. 10-12 hour burns are easily done with favorable weather conditions. what more can you ask for??

Now, when i fill the basket 3/4 or more i have a problem with heavy white smoke. its not a solid plume of smoke, but it is heavy enough to leave creosote on the food and doesnt have that sweet smoke aroma. what am i doing wrong? i have read many threads of people boasting about 20+hr burns with nothing but sweet blue awesomeness puffing out the stacks. one fella even said he gave up after a 24hr test that held 200f :shock:

i did notice that when the basket is filled 3/4 or more, there is a top layer of unlit coals. is this my problem? too much fuel for smoker at the target temp? i'm guessing the top layer is not lit due to the lack of oxygen because i dump lit coals on top.

Is there something i'm overlooking or doing wrong for these full coal basket burns???

my last cook was a 20lb ham leg and didnt want it to burn out. so yes, i wanted a longer burn with out having to add fuel overnight. Outside temps have been dropping into the 30's so i only open the lid when neccesary

the lump charcoal isnt damp. i have already ruled that out.

with such a full basket, do i want the whole top layer to be lit coals? smoldering unlit coals is a possibility. can i expect all of the 10lbs of lump to remain lit while maintaining 250F-ish.

i forgot to mention that i had already cooked a 8pcs of chicken and 4 yams for 2.5 hours before i switched over to the ham leg. is it possible that the juices and fat from such a large piece of pork are quenching the coals?

i appreciate all the input!

one time i put a coffee can filled with holes in the middle of my basket thinking it would prevent smoldering unlit pockets in the center. what i found was that the lit coals worked their way around the can beginning at the wide open intake port. had thin blue smoke all the way.

i think i'm getting close to the answer here. correct me if i'm wrong, i'm a greenhorn, but having unlit fuel underneath and next to the coals is ok, BUT having unlit fuel ON TOP of the coals is no good.

do i need to start with more more lit coals? a large coffee can is maybe 1/2-3/4 the size of a store bought charcoal chimney.