Overclocking is not recommended on that board, its vrm's overheat fast due to no heatsinks, causing system instability. A small overclock might be possible, but 4 ghz is pushing beyond the boards' limits.
I think you would be able to overclock it if it's cool enough, i don't know how much the motherboard comes into it as i've never done it though :/ but you're on AMD the same as me, download AMD Overdrive and if it lets you, then i guess you can!
Overclocking is not recommended on that board, its vrm's overheat fast due to no heatsinks, causing system instability. A small overclock might be possible, but 4 ghz is pushing beyond the boards' limits.