Rocker Arm Asembly
 

I ran into an indy MB shop today. The svc mgr told me that right around 180k miles the metal alloy starts wearing off the surface of the rocker arm causing the cam lobs to wear down. He says it's common in 420's. He says a cam job is $2000 and replacing the rockers is around $500. I wanted some feedback on this, before I look any further. Does anyone have any opinions on this.

Sounds kinda expensive if you ask me. I had my cams in my 86 420SEL replaced at 80K and the dealer only charged me I believe well under $1000. The rockers sounds ok, they can be pricey to replace all them. If its not that loud, I would live with it.