BTW - my plan is to serve around 6:30 pm
As others have mentioned, I also would not bother running at 160-170F smoker temp. That is simply too low to get a brisket cooked in time, they take forever. Also there are food safety concerns. Cranking up the heat resolves both situations.
So at 275F, unwrapped the whole time, I would put that 14 pounds of brisket on at 10-10:30pm the night before.
****IMPORTANT: The number 1 failure of people doing briskets is that they pull the brisket off before it is tender (done) and that is usually caused by :
1. Running out of time or improper time estimation (Not enough time planned)
2. Going by temp of the meat or going by time cooked rather than tenderness of the meat to indicate when the meat is done
It is never a problem to finish early. Even if you finish 6-8 hours early. You can always hold the meat keeping it hot until time to eat.
However there is nothing you can do to correct having to finish late. The meat tells you when it's done and if you don't listen well you get dry tough meat because the collagen hasn't broken down.
How do you check to know a brisket is done????
Put your thermometer probe in the thickest yet center most portion of the FLAT muscle. Not the Point muscle.
When the thermometer reads 198-200F for the Internal Temp (IT) of the meat then you check for tenderness.
To check for tenderness stab all over with a kabob skewer and when it goes in ALL OVER with no resistance well it is tender. If you find a spot with resistance then wait for the IT of the meat to go up 1-2F degrees and then check for tenderness again. Do this until it is tender. When tender it is done!
Let me know if this makes sense and please ask if you have any questions. You are attempting what may be the most difficult meat you can smoke. It is only difficult if you aren't well educated and prepared to take it on. Once you succeed you get better with each attempt and then you perfect it to your liking in no time!! :)