There has been some discussion on this in other topics, even going a bit further, whether V4 or the ‘zynductor’ would be enough cooling to allow 2GHz overclocking.
To ‘cut to the chase’ from @ jofemodo:
If you have V4, you could use overclocking carefully, given that the zynductor is well installed. If ambient temperature is low-enough you shouldn’t have problems when using maximum speed (2GHz), but be warned that you probably would have problems if ambient temperature goes beyond 20ºC.
If you keep an eye on system temperature by refreshing webconf’s dashboard, you could change to a lower overclocking profile when temperature goes higher than 60-65ºC.
So… if you added more cooling, like a fan, you could survive at even higher ambient temp.
For the fuller discussion see:
and:
and for even more, search on “zynductor”