i hate to disagree with anyone, but something else is going on with your CPU. those load temps are a tad bit high. i have always been able to get stable, reasonably high o/c's even with the junk stock coolers that come on i3 CPU's.
here is a little rule of thumb. running you memory multiplier at the correct ratio for your desired memory speed and cpu speed is critical in getting a good o/c at low voltage. temperature is the byproduct of voltage (that's why they are still called semiconductors).
you should be able to hit 4.0-4.3 ghz. well under the MAX cpu voltage, and you should be able to do that on the stock cooler.
what memory multiplier are you running? and then what uncore are you running?
rule of thumb for x58 is 1.8-2.0 memory to uncore
for example, let's say you have a memory ratio of 10, your uncore should be around 20
also the higher your memory multiplier, the lower you can pull that ratio
for example....a memory multiplier of 12 and you could pull your uncore down to around 22
this will equal less vtt for the same o/c of your CPU.....the downside will be a slight hit in memory fill rates and round trip latencies....
of course each CPU is luck of the draw, but you shouldn't be anywhere near the temperatures you are showing, with that low of a vtt on the CPU....
70c for 1.2 vtt is not normal....something else is going on....
if anything you might be under volting your CPU for the selected uncore/qpi/mem. multi
if you can tell me your settings in BIOS I might be able to help you diagnose if you in0fact do have a problem with your cooler/tim/cpu
