Can't overclock on my motherboard even though overclocking is supported?

Oba Adelaja

Honorable
May 26, 2013
8
0
10,510
HI everyone.
I have been trying tro overclock my i5 3570k now for almost 3 months (on and off) but although when i change the multiplier and voltage in my bios, when i get into windows and check cpu z it shows my settings a default. I am aiming to get a moderate overclock of around 4.3ghz please help!

My system Specs:
i5 3570k
Ecs z77h2-a3
Radeon hd 6870
WD caviar green 1tb
Powercool 650 watt power supply
2x8g 1600 ram

Thanks