I mounted my swiftech block and the screen on my monitor was black upon talking with Gabe he mentioned a possible solution and it worked so Iam sharing.
The cross spring that goes behind the GPU should not be tightened all the way snug. Instead tighten then back the screws off 1-2 turns to relieve some excess tension on the GPU. This solved my Black Screen problem.
Hope this helps other of this forum.
