Intel i7 4790k stock cooler temp advice?

The stock cooler is fine. The main negative is that the small 92mm fan will spin up and get noisy under load.
Try stress testing with occt. It will shut down the test at 85c.
No damage will happen from overheating. The cpu will simply downclock or turn off if temperatures reach 100c.
I have become a bit jaded on the subject of haswell cooling for overclocking.
How high you can OC is firstly determined by your luck in the bin lottery.
I had high expectations from the Devil's canyon parts and their better thermals.
I found out that the thermals really do not matter unless, perhaps, you are a competitive overclocker.
Haswell runs quite cool, that is, until you raise the voltage past 1.25v or so.
Once you go past 1.3v, then you really do need very good cooling to keep stress loads under say 85c.
But, the consensus is that voltages higher than 1.30 are not a good thing for 24/7 usage.
I have been unable to find any official Intel recommendation on what is a safe vcore limit.
If you are an enthusiast, you can go higher.
Even if you can handle the heat, how much do you really need that extra multiplier from say 4.4 to 4.6?
My thought is that it is better to use the exotic cooling funds for a quieter and less expensive air cooler.
I suggest a good tower air cooler like noctua or phanteks with 140mm fans.

My canned rant on liquid cooling:
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You buy a liquid cooler to be able to extract an extra multiplier or two out of your OC.
How much do you really need?
I do not much like all in one liquid coolers when a good air cooler like a Noctua NH-D15 or phanteks can do the job just as well.
A liquid cooler will be expensive, noisy, less reliable, and will not cool any better
in a well ventilated case.
Liquid cooling is really air cooling, it just puts the heat exchange in a different place.
The orientation of the radiator will cause a problem.
If you orient it to take in cool air from the outside, you will cool the cpu better, but the hot air then circulates inside the case heating up the graphics card and motherboard.
If you orient it to exhaust(which I think is better) , then your cpu cooling will be less effective because it uses pre heated case air.
And... I have read too many tales of woe when a liquid cooler leaks.
google "H100 leak"
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