I'm currently fighting a nasty knocking sound on my Northstar powered Lucerne CXS and I've been looking at heads on eBay. It seems there are two varieties of heads for the Northstar... those with tappets where the cam is in direct contact with the tappet and those with rocker followers where the cam is actuating a follower with a roller tip. Can anyone explain the difference and which vehicles/variants of the northstar used which type of head configuration? I see a lot of confusion in the forums regarding the language and terminology. My Lucerne shop manual describes the heads as though I have rocker followers but when I pulled the valve covers my Northstar has tappets. With the tappet configuration there are no visible valve springs. Did someone do a motor swap on my Lucerne before I bought it or is the factory shop manual just wrong?