My contribution to this thread......

I dyno tested a 557 BBM with -1 heads on it that the owner was trying a vac pump on.
He had the fitting in the valley cover.
We had made several pulls with valve covers that had breathers and no belt on the pump.
Swapped covers and hooked up the belt.
I barely got to WOT and the puke tank was over flowing.

Took the hose off the puke tank and had it aimed into a bucket.
At WOT it looked like a fire hose amount of oil coming out.

Valley cover = Not a good place for the fitting.