I've taken my 2100+ 'b' core to 2800+ spec with out hassle. I did have to increase to voltage to 1.85 though. no real temperature change to be worried about, it idles at 41 degrees with the case side off. All cores are individual, some need more voltage others not. trial and error is the name of the game. just raise it one step at a time until it doesn't lock or give any other hassles.
P.S. I've set to 166 x 13.5 with a vcore of 1.85 perfectly stable. good luck