The BLCK is the Base Clock.
It has a Impact on everything.
Basically what you want to do is downclock your memory.
For example, if you want your RAM to run at 1333, set it to run at 1066 speeds.
Depending on what CPU clock you are shooting for, you RAM will most likely end up being where want it by the time its all said and done.
What I would do, is just set the RAM as slow as you can possibly get it to go, and work on your CPU clocks.
Find out what voltage and BLCK you need for for the CPU to be stable.
Once you find where you want it to be, lower the CPU multiplier, and start again with the memory.
This method help pinpoint problems, because you are taking one variable out of the equation.
This way, when Prime or IBT fails, youll have a better idea as to whats causing the issue, because one will be running well below spec.
Just keep an eye on temps (especially with IBT!), and depending on your RAMs rated speed, keep an eye on what speed its ending up at with BLCK changes.
Ideally, you want to keep it at or below rated spec.
Also, if you have 1333 rated RAM, its possible you will find your RAM having issues before the CPU actually does.
Loosening up timings may help a bit if thats the case.
Have fun, and just be patient
Takes time to figure out where everything is happy playing together.