Why my system crashes when I try to overclock my GTX 1070?

[ProPlayerGR]

I have an Corsair 650VS power supply.
My PC specs:
CPU: AMD FX 9370
GPU: INVIDIA ASUS GEFORCE GTX 1070 FOUNDERS EDITION
MOTHERBOARD: ASSROCK 990FX EXTREME9
PSU: CORSAIR 650VS
CPU COOLER: CORSAIR H100I
RAM: CORSAIR VENGEANCE PRO 16GB 2x8GB
HARD DRIVE: SSD 240GB
CASE: CIT APACHE GAMING CASE-GREEN
So my questions:
1. I think that my power supply is good for my system so why my system crashes when I try to overclock my GTX 1070?
2. To overclock my GPU what do I have to do?( I think that I have to high up the core speed but I'm not sure. It may be that I high up up the wrong thing to overclock my GPU and my system crashes).
P.S. I use MSI Afterburner to overclock my GTX 1070. Thanks for the help.

 

[turkey3_scratch]

1) Your PSU is a budget unit. Your system is not budget. Your PSU isn't that good so it could very well be the cause of why overclocking is not going well, especially considering it's an old group regulated design.
2) Sometimes you just can't overclock it. If every GPU in the world could achieve a stable overclock they obviously would sell them out of the box with those higher clocks.