Hey guys, I'm having the same problem, and I'm using the same setup an i7 2600k with a corsair H70 in a CM HAF 942 case.
At a VCore of 1.2 and a clock of 4.2 GHz I'm getting temperatures of 70C under full load, which isn't bad but is limiting my OC potential. I can get it to run stable at 5.1 GHz, but only at temperatures WAY in excess of what I'm comfortable with (95+ under load)
My push/pull setup is working, I've checked that the cooling block is in proper contact with the core, and I haven't used too much TIM.
The other weird thing is that while Cores 1, 2, and 3 all seem to be within 1-2 degrees of each other, Core 0 is always 8-10 C cooler. I know that a 3-5 degree gap can occur, but 10 seems excessive.
Am I missing something stupid?