my gtx 460 is factory oc at
- Core Clock: 715Mhz
- Memory: 1024MB GDDR5
- Memory Clock: 3600MHz (Effective)
I highly recomend you go to the MSI website and download Afterburner overclocking utility. This works withany brand of GTX460, though Im not sure if you will be able to use the voltage increasing sliders. I have my GPU voltage all the way at max, my mem voltage +70, and every review I have read says dont increase aux voltage because it has no effect.
I run the GPU at 925Mhz and mem at 2000 so 4000MHz effective. You should start around 825 - 850mhz for the GPU, keep the shader locked with the GPU, and memory would easily do 3800 to 3900.
http://www.bit-tech.net/hardware/graphics/2010/07/21/overclocking-nvidia-s-geforce-gtx-460/3
you can use kombuster tool to test your oveclock and look for artifacts. The DDR5 RAM on these cards will slow down performance themselves if they are clocked too high, so if you see performance drop, scale it back.
http://downloads.guru3d.com/MSI-Kombustor-(Furmark)-0.7.0-Beta-download-2461.html
GPU to high will usually crash in a game. If you have the reference heatsink I wouldn't go too much over 875 to 900 if I were you cause the fan will be louder.
Another good method is look at the cards for sale on newegg, you can usually get the same overclock on anything that matches the highest offered factory overclock. That is always a safe starting point.
Good luck!