Originally Posted by CelticGamer
This turned out to be a fantastic piece of advice. I went ahead and removed the PCIe slot covers, four of them, and my temps started to drop dramatically. Apparently, I just wasn't getting good ventilation out the back, probably due to the 120mm radiator installed in the rear.
Keep in mind case airflow is determined by the smaller of intake or exhaust airflow potential. A case only flows as much air as the smaller of the two. So if exhaust vent area (with or without fans) is only 1/2 the size of intake area then the case's airflow will only be as much air as can exhaust through the exhuast venting. Most cases have lots of front and top venting, even bottom venting, but I can't think of any with more than 1 fan vent in the back.
By removing all PCie slot covers you opened up at about another fan's worth of vent area and improved the front to back airflow around GPU and thus move it's heated exhaust air out the back much faster.