Which model Corsair RAM is it. Big differences between vanilla, vengence models and dominator models (even differences between some sub-brands). Also, what speed and voltage is it labeled for?
Unfortunately there is no good answer for your question even with the above info. RAM is notoriously fickle and what works for one pair may or may not work for another.
In general, best OC will be achieved at 1.65V (absolute maximum), then keeping stock timings and bumping up the RAM speed until it doesn't boot. Then return to stock speed and try the same thing lowering the timings instead until you get something that doesn't boot. Then use this chart to compare which is fastest in your case...http://i1013.photobucket.com/albums/af254/Jaquith/CAS_Frequncy_Chart.png
My guess is that if you keep stock speed and bump up the voltage then you should be able to hit around 7-8-8-22 or so. Fiddle around with 1T vs 2T also, but more than likely you'll be stuck with 2T as DDR3 just doesn't seem to like running at 1T in my experience. Keep in mind (see chart) that this isn't really getting you a whole lot, especially in terms of real world performance. The memory OC ship sailed along with the dissapearance of DDR2 a couple years back. It just doesn't matter anymore.