[vector1]

you can vent with no problems, if you run a closed crankcase you should put some type of regulator in, or provide for it, or the possibility of pulling too much vacuum which the consensus is anything above about 12" can be detrimental to the engine. the size of the pump sections also has an effect on how much vacuum you will pull. with my 3 scavenge sections i can pull around 5" running at 2000 rpm, so i do run a vacuum regulator. i have also owned a race car from a knowledgeable individual that used an open system, with a breather, so either way imo, whatever works.