I always recommend using more fans to take heat out than taking heat in.
I tried before to use the bottom 120mm fan on my corsair 750d and it was worse in therms of (120mm fan weaker than 140mm and dust was gone in).
Yes I recommend to use 2 intake and 3 exhaust.
2X140 in front. 1X140 in the back.
CPU cooler with the fan on the back or on the top (not really matter) - exhaust. 
Additional airflow fan 140mm on the back or top.
Attached my case waiting for my 1080 
 

 

gregoryv
I always recommend using more fans to take heat out than taking heat in.
I tried before to use the bottom 120mm fan on my corsair 750d and it was worse in therms of (120mm fan weaker than 140mm and dust was gone in).
Yes I recommend to use 3 inbound and 2 outbound.
2X140 in front. 1X140 in the back.
CPU cooler with the fan on the back or on the top (not really matter) - exhaust. 
Additional airflow fan 140mm on the back or top.
Attached my case waiting for my 1080 
 

 

But you have 2 intake and 3 exhaust unless you have the top trying to pull cool air in. You have a negative pressure case which will cause it to suck air in thru the cracksand cause more dust inside your case.

What you need is custom water cooling :)

karloy

ragevirusqq
I would save a few dollars up and buy a new case. Its a shame to choke that sli setup with not enough airflow. Great airflow cases can be had for less than a hundred bucks. Corsair air 540, Fractal design define s, NZXT come to mind. Corsair cases can be found at Frys too if you have one near you. There is lots of good options even in the 60 - 80 dollar price range.   
 
You have great gear in there. It just needs a nice comfy place to live. 

Alright, after plenty of research I am going to upgrade my case to a Corsair’s Graphite Series 760T. My old case has airflow issues per reviews. Going to have 2 x 140 fans in the front, one 120 at the bottom, Asetek 510LC 120mm fan in the back, 140 fan at the top. Hopefully that will do it ;-)

 
Usually positive pressure is best for cooling your PC
 
Did you look at Cooler Master HAF 932 Advanced case - I really like mine - talk about airflow
 http://www.newegg.com/Product/Product.aspx?Item=N82E16811119160
 
 
 
I Did NOT like my Corsair 760T airflow    for my EVGA 980 SC ACX in 2-way SLI setup

ragevirusqq

karloy

gregoryv

karloy

ragevirusqq
I would save a few dollars up and buy a new case. Its a shame to choke that sli setup with not enough airflow. Great airflow cases can be had for less than a hundred bucks. Corsair air 540, Fractal design define s, NZXT come to mind. Corsair cases can be found at Frys too if you have one near you. There is lots of good options even in the 60 - 80 dollar price range.   
 
You have great gear in there. It just needs a nice comfy place to live. 

Alright, after plenty of research I am going to upgrade my case to a Corsair’s Graphite Series 760T. My old case has airflow issues per reviews. Going to have 2 x 140 fans in the front, one 120 at the bottom, Asetek 510LC 120mm fan in the back, 140 fan at the top. Hopefully that will do it ;-)

Good choice. Corsair 760T is great case. I am having 750D flow edition and it is great.
You don't need to use fan on the bottom.
You have 2x140 fans on the front and 1x140 fan on the back coming with case.
Also you have additional place on the top to put CPU cooler and fan. I would add addition 140mm fan on the top to take the hot air out.
I think it will upgrade very much the flow inside the case and temperatures on the both cards will go down.
 

Very helpful, thanks for the advice. I have 1x CPU fan, and 4x case fan plugs on my board. 
 
What is the ideal inbound/outbound fan ratio? 
 
You are recommending: 
 
Bottom: None
Front: Two fans (already installed) - inbound
Back: Fan (already installed) - outbound
Top: CPU cooler fan + additional fan - outbound
 
(2x inbound, 3x outbound)
 
I wanted to do the following: 
 
Bottom: Fan - inbound
Front: Two fans (already installed) - inbound
Back: Fan (already installed) - outbound
Top: CPU cooler fan - outbound
 
(3x inbound, 2x outbound)
 
First time configuring this ;)
 
 
 

just remember to stay positive. either more intake fans or reduce the speed of the exhaust fans to keep positive airflow.  This will help elimate dust which can cause other potential issues. 

Okay, so this is a vote for the second configuration, have the intake fan at the bottom. 

chrisdglong
ACX are bad at running in SLI, end of story. I tried everything and my top card still ran hot. Send those back for a couple of FE cards... It is the reason that I did not buy an ACX card this time around, because I want the option to SLI. I bought the FE. I learned that ACX is great for single card situations, but TERRIBLE for multi-card situations. 

No, they are not. Quit spreading bad statements. Get a bigger/better case, get better fans. If you're overclocking the cards, back off of that too. Watch your cards magically go back to decent temperatures.

Glad to hear you solved it ;)