Better the cooling the more vcore you can put to it . Up around 2.9ghz you will more than likley need to bump the vore to the 1.50 range and thats where the temps are gunna come into play with stock cooling . Just for reference i need 1.6 for 3.0 ghz , ive seen some higher and some lower.
If , or when, you pull off the stock heatsink/fan , look for the stepping on the cpu itself , look for something like KABCE it will help when comparing your overclock to others. Good luck