I had a Tuniq Tower 120 Extreme mounted on my i2600K blowing air up. The heatpipes on this heatsink were vertically oriented and spanned a height of about 100mm.
I noticed that tipping my case forwards 90 degrees so that the heatsink's heatpipes became horizontally oriented dropped my temperatures by about 3C after a couple of minutes. The difference was detectable repeatably and I kept the case's front fan blocked while checking. So I remounted my heatsink with a 90 degree different orientation, blowing air out the back instead of out the top and with horizontally oriented heatpipes. Now under 8 thread Prime95 load I get about 54-55C at 4.4 GHz instead of 57-58C.
Does anyone have a similar experience with their heat pipes?
If this effect is generally true, it would be nice to put that in the sticky guide here.
The effect probably depends on the particular heat pipe type, so it may not be universal. There are some coolers that you can't use in certain alignments because it would cause the heat pipes to not work at all, or not as well.