Only the Clarkdale i3s on LGA 1156 were really overclockable. Starting with Sandy Bridge, you need to have an unlocked multiplier to really overclock Intel CPUs. Changing the BCLK speeds won't work because that bus speed is tied into all sorts of other motherboard devices, and making any significant changes to that clock will make the system unstable. Some people have had some luck playing around with Turbo Boost settings on the locked i5s and i7s to get a modest overclock, but i3s don't have Turbo Boost, so you don't even have that option.
If you want more CPU performance, your only real option is to buy a new CPU.