Dual-processor graphics cards are generally not very good at overclocking as they have complex PCBs and high power requirements and need efficient cooling. The EVGA GeForce GTX 560 Ti 2Win is no exception. Its GPUs could only be stable at a clock rate of 870 MHz or 2.4% above the default one. The graphics memory did much better, speeding up from its default 4008 to 4800 MHz.
The card even passed all the tests at a memory frequency of 4920 MHz but showed some visual defects in Aliens vs. Predator (2010) and Unigine Heaven Demo, so I had to limit myself to 4800 MHz to be on the safe side.
When overclocked, the graphics card grew 2-3°C hotter in terms of the temperature of its GPUs. The speed of the fans was only increased by 150-200 RPM in the automatic regulation mode.