Read a Tom's Hardware guide on over clocking. There is no set number than any CPU can reach. It might not be stable at 4.3ghz. It might make it past 5ghz.
There is a reason that people spend a lot of time trying to find the highest stable overclock on their parts.
If there was a way to just look at a CPU model and know exactly what the overclock would be we would all have the max overclock on our CPU in 5 mins and this whole section of the forum would be a ghost town.
Learn more about overclocking before you attempt to.