IMO you can't (until laws prohibit  ) Have too big enough Breathers on these motors  but to blow a breather like you describe suggests alot of crankcase pressure , could be a number of things Tom

This is not a common problem with a solid roller high rpm motor. Some will weld a bung in their exhaust and run a hose from valve cover to the exhaust so the blow by just fly's out the exhaust on both sides. I went the more expensive way and ran a vaccume pump witch sucks the blow by out of the motor and spits it in a catch can and is adjustable and you'l see a 20 hp gain with the pump style. my old motor would spit oil out both k&n breathers in the valve covers and it would make a mess and piss me off.it reved about 6600. I'm talking about motors pushing 5000 2 8000 rpm's tho. I don't think that is your case tho. I'm not sure if this will help you but Im letting you know that crank case pressure in not uncommon, and on most big hp motors they will run one of the two set ups Iv'e described. The vaccume pump is the best way to go in this case. i will post a picture of my next post of what it looks like. all said and done i spent around a 1000 or 1200 for the complete set up which is why most just dump out the exhaust. In your case it could be a ring problem not sealing and pushing oil fuel or exhaust into you valve covers and tho only place for it to go is out the valve cover breathers.