It's possible, yes. I have an EVGA GT 240, which I tried overclocking. I didn't go all out on trying to OC it because in my situation it ended up not making a big difference, but I found that it seemed to get up to around 700-750mhz core and only about 1730 or so memory (I had core and shaders linked).
Probably possible to get the clocks higher.
Download MSI Afterburner to mess with the clocks, and then run either Kombustor or FurMark to test stability and temps. If there's artifacting or a lot of tearing/pausing you need to lower clocks... try raising memory first, then core and see what happens. It's mostly just trial and error so good luck