1. rad-dance depends largely on the make and model. Alphacools are notorious for being "dirty", Phobya's also tend to be dirty (same OEM). Aquacomputer AMS & Watercool HTFS are extremely clean (by design) and only need a dust flush.
But in general :
- 10% white vinegar or a (small) teaspoon of citric acid in near boiling (tap) water and pour the mixture into the rad..
- let sit for 10 minutes or so (until you no longer burn yourself on the rad)
- shake vigorously
- repeat 2x or 3x times (or more -until there is no longer gunk coming out)
- fill with (new/fresh)distilled
- repeat a few times (till it no longer smells of vinegar)
2. optimum block orientation depends largely on the make/model of the CPU chip, although it doesn't make that much of a difference.
Several tests have been done, but I don't have the link & whom at the top of my head. But if you search this board fro Supremacy EVO orientation, you probably find something like "10 blocks tested"