20 pound chuck roast

monti,
at around 185-190 internal take your beef out of the smoker and wrap it in foil. it will easily go to 200 just resting.
as far as time goes to be safe figure on the 1.5hr/lb. but your surest way is to use a remote thermo and set your alarm for the 185.
taylor makes a good one and target sells them for around 15 bucks
hoe this helps some
jack

Monti,

Sounds like you might have a chuck roll, which run about 20#, and are what they cut the chuck roasts from. If you cook it as a whole, the inside meat probably won't have much of a smoke taste and it'll take forever to cook something that large.

When I cook a chuck roll, I cut it in thirds so there are more surfaces to absorb the smoke, and so it gets done more quickly. So in your case, you'd cut it into three 6-7 pound chuck roasts.

I then cook it like pork butt, taking it up to about 195* internal, and it should take about 14 hours (2 hours per pound for your biggest roast, assuming the biggest ends up about 7 lbs.).

You can search these forums for "chuck roll" to get some other ideas on how to prepare your 20# beast.

I'd probably go with Studly's recommendation. I had a 4lb'er take 9 hours, but it was sooo good. Pulled like pork, and tasted great. Just don't oversmoke. Good luck!

Monti, I did about a 16 lb chuck a few months ago on my model 55. I think I did cut it in 1/2 just to fit on the shelves and get more bark. I would go to at least 195-200 then let it rest in foil a few hrs. The very thickest parts of mine did not completely pull but the rest was great. Froze some. I don't think the rub makes much difference as is will not penetrate much. I have been sticking to Montreal Steak for brisket lately and avoiding rubs with sugar on beef. (just my preference.) Most of the flavor would be from any sauce you serve with.

Thanks for the advice. I am really looking forward to this long weekend, and a great smoke.