It be tuff but one thing I did that made a difference was adding a extrenal fan (120) blowing in from the backside of the case where the ports are on the cards. One would have to remove the blank slot plates from between and below the bottom card to allow the air to blow in. That's cool air blowing in for the cards heatsinks that lowered the tempts of both cards by 6c atleast. Might be more for someone else where there not getting any air circulation around the cards at all.
It all depends on your case if you can figure out a way to mount a fan there.. I just used a long zip tie and looped it threw the fan mount hoes and an opening on the case to hold it there.
Make sure the fan is the sticker side facing the case as that the direction the fan blows.
That's why I say evga's new pc case with there dual 120mm fans on the left side that exhaust or blow air into for your graphics cards would be great for hot air cooled graphics cards.
Other then that I ran with also a fan on the other end of the cards blowing air to them.. so I had air blowing at the cards from both ends.
Don't want a fan blowing at them from the side cause the fans on those cards blow strong air straight out from the side and down to the motherboard. So it would be useless.
Heat rises so good exhast put the top and strong cool air in from the front that blows towards your hot cards would be best..
No idea how the fans are setup in your case with that corsair cooler. Is that a single fan cooler for the cpu?? Mounted to the left of the cpu?
You need to test those cards ea with just one card installed at a time. Hopefully you can do that.
All you need to do is first thing disable sli in the Nvidia config. Then turn the system off. Flip the power switch on the back of the pc power supply to off.. and pull the plug from it as well just to be sure. Then hit the power button on the pc to drain all the remaining power stored in the caps from the PSU and mb.. you'll see it attempt to power up and the fans will slightly spin and shut off.. if you wait about 30 secs the power will drain from the mb and that wont happen when you hit the power button.
Then remove the side panel from your case. Remove the sli cable. Then pintch and pull the power cables from the graphics card your removing.Get a screw driver and remove the 1 or 2 screws holding the graphics card at the PCIE slot holder on the left. Now there's a small lever that locks the graphics card into the PCIE slot on the mb on the right side of the cards slot where it goes into the PCIE slot on the motherboard.. press that down and your card will then be free to pull straight out.
Might wana hunt for a video on YouTube for how to remove or install your graphics card if your confused.
Then plug the power cord back in to the PSU and power the pc up. Should not have to Install any drivers since you only removed one card.
Test that card.. it should run cooler now.
Right down temps.. idle and boost clocks and for the fun of it your benchmarks with just one card. And now you can test the cards max overclock. Don't bother overclocking the cards memory as it can limit your max cpu core overrclock.
Then when you think you've found the max you can get without locking up right that down.
My best benchmark is to use 3dmark firestrike. It's safe to use cause usually if your not stable the graphics driver will just error and then the benchmark will just end and no damage to whatever game is runing or lockup that needs a hard reboot.
Plus you can run a custom loop for whatever test. I like firestrike custom where I can select to loop just graphic test 2. So no loading in between changing tests for max heat.. if it will run that test for a half hour or more then you know your overclock is stable.
You can also buy 3dmark through steam.
So anyways when your done testing that card and also tested it with a few games for the black screen 100% fan issue, remove the card and swap in the other one and repeat all the tests keeping notes on that one.
Then when your all done and you noted each card by the last 4 serial numbers.. install the best card into slot one and the other in the other slot.
You really need to test ea card seperate.. it's also important cause you may find out one has a bad thermal goop job or a loose heatsink not making proper contact and could be why it's runing so hot.