"Likewise, EVGA understands that enthusiasts are not always satisfied with the provided stock cooling options. Replacing heatsinks, fans, or thermal grease will NOT VOID your warranty. Want to install a waterblock on your new motherboard or graphics card? No problem. Planning on a long benching session with a DICE/LN2 pot? Good luck on the benching, but your warranty will still be intact after you’ve set new world records.
Of course, there are some limitations to our warranties. If an EVGA motherboard or graphics card sustains physical (i.e. damage to the PCB or component due to slippage with a hand tool) or liquid damage, the warranty is void. Similarly, permanent changes to components or the PCB will void your warranty, including the removal of pre-attached components soldered to the board, or the addition of components that are not removable without heat or solvents. In other words, you may use Precision X1^TM to raise the voltage on your graphics card while overclocking, but you may not solder on another power connector as an alternative."
 
This is from the FAQ Help Center (sorry, I don't know how to include a link to it.)