Installed a new cam, now it smokes... Why?

your new cam is pushing your valve,s a bit farther & a bit longer...valve,s have a tendency to wear at the guide,s or build up crap at the point where they used to stop...now they're traveling just a bit farther in effect destroying your valve seal,s & possibly guide,s. allowing oil to seep down & burn...remedy?...install new valve guide,s,seal,s. or go for a set of performance head,s...loaded that is.....best of luck!