Sure I can and no my RPi don't use any active/passive cooler. Under load on these hot days (in room temp 30°C) the max temp I have seen with closed case was 67 °C. http://haydenjames.io/raspberry-pi-2-overclock/ < a good beginner article about overclocking the RPi2 
---- arm_freq=1100 core_freq=500 sdram_freq=480 over_voltage=4 temp_limit=75