Core Voltage not working in MSI Afterburner?

[IsFyx]

So, I'm trying some GPU OC for the first time, using MSI Afterburner on a GTX 670. I've got it stable at +155 core clock without raising the voltage or power limit at all. However I'm a bit confused as to how to proceed.

 

I'm not experienced at this, so call it out if my rationale is wrong:

Firstly, I don't want my card to be too loud, so I figured out what my preferred max fan speed would be. 70%

Secondly, I don't want it running much hotter than 75 C, so i set up a fan curve that ramps up from 10% under 50 C, to 70% after 70 C and 100% after 75 C. While tuning the card I set it to a constant 70%, aiming to not get it over 75 C at that speed.

 

I proceeded to step up the Core Clock until i found the point of instability, somewhere between +160 and +170. I then went on to try to step up the power limit, as I've heard that is preferable to stepping up the core voltage. That didn't do much, so I went on with the core voltage slider. However, at this point things start to smell a bit fishy, as I'm maxing out the core voltage slider and my temps still won't go over 59 C. Checking the voltage to the core I see that it's still at 1.175 V, which I believe is the stock setting.

 

So my questions is as follows:

 

What am I doing wrong?

If I get it to actually raise the voltage, how high is it safe to go?
Do i just keep cranking it up until i get my desired max temp, or should I stop at a certain setting?

What is the actual difference between Core Voltage and Power Limit, and how do they work?

I was told to just keep raising core clock and voltage until I hit my max, and then proceed to memory after. Is that the best way?

 

I'm using Heaven at extreme preset to push the GPU. It hits 100% load, but never goes above 59 C.

[Face2Face]

Max Voltage on a GTX 670 without modding is 1.175v. That would explain why you're not seeing anything higher.