smoke coming out of valve cover breather

Hi guys i bought this engine a while ago from a user on this forum

http://www.hughesengines.com/TechArticles/4feb2008smallblock426strokerdynotest.php

first it wont start up so we changed everything a new distributor , spark plug wires ect...

The engine runs now and sound very strong but my problem is that alot of white smoke come out from the valve cover breather on the left side at the right side also from the valve cover plug i also do have a pcv valve and its installed but not the line yet, because i need to drill a hole in my intake manifold first, i run a 15w 40 oil, the guy runs the engine with NOS somethimes i dont hope that a piston is gone, i also do have a compression tester, i need do check that too, but maybe some of you guys knew whats my problem is maybe

Thanks Peter