Sirloin tip roast question

Sirloin roasts smoke best at a low temp, 225-250F or so.  It allows more smoke flavor to build on the roast and keeps the outer edges from getting well done.  You get a nice, pink consistency through the whole roast. 

Unfortunately it won't brown the roast like a higher temp will, so a hot sear at the end of the smoke, called a "reverse sear," browns it up nicely.  It's an eyeball kind of thing. 

At 225-250F, an 8 lb roast will take around 5 hours to hit 140F, give or take.