FX-8320 Prime95 test questions.

I am trying to find a stable overclock for my first PC but I am unable to run Prime95 on all 8 threads for more than 5 min. before my CPU temps get to 80c and I shut it down. I primarily game so would it be acceptable to run prime95 on 4 threads to simulate most game CPU use?

Mobo:m5a99fx Cooler:hyper 212 evo GPU:msi 270x CPU:FX-8320 PSU:FirePower OCZ ZT Series 550W