smoke in the top of the head?

what would cause my car im tring to put into time to be getting rather large amounts of smoke under my valve cover? im working with an 8v VW but i id imagine it could happen on any car. but whyy?

smoke in your head? spend less time with darkstar.

blow by?

i thought that only refered to piston ring blowby that would end up in the crankcase?