you are wasting your time. the only thing that is holding back a GTX 970 from going faster is the max power target and voltage offset.
i have a pair of MSI GTX 970 gaming cards. even with voltage and power target cranked up to the max, i never went over 65*C even under 100% load. and i can't even hear the card's coolers over the gentle whisper of the H110 cooling my CPU.
the reference boost speed for a GTX 970 is 1178MHz. mine are running at 1500MHz. that's a 27% overclock. and i have no doubt in my mind that they can go faster if the BIOS would allow the higher voltages.
the only thing you will achieve by water cooling a non reference GTX 970 is that you will make it louder, spend hundreds of extra dollars and burn several hours of your time. that's it. if you want a faster card just buy a non reference GTX 980 and overclock that.
only if you can bump the voltage by 150mV and set the power target to 150% will water cooling become useful.
otherwise, if you are simply hellbent on water cooling something, pick up an R9 290x. those guys go pretty cheap these days and they actually need the water cooling.