no idea
every cpu is different. the overclock you get on one isn't a guarentee of an overclock on another. generally Vishera chips should get to 4.5 without any issue at all... after that it comes down to your motherboard, psu, and how lucky you were with the cpu.
I've seen most people are able to get up to 4.8 if they work it... around 5.0 or 5.1 the vishera gets a bit unstable. i do know a guy who was able to get his up to 5.5 with an overclock for everyday use. But he had a very robust cooling system and motherboard, and he admitted it was oddly unstable from 5.2 to 5.4, he just kept pushing higher to see how high he could go. And fell into the strangely stable 5.5
The point of all of this is, to say "you can't tell till you...