Knocking noise in 84 190E
 

My 190E in the morning and at idol has an awful knocking noise. It's more prominent in the morning on a cold start. It seems like it's coming from the front part of the engine. I'm not sure. My dad said it could be the timing chain which i do believe is costly to replace. But I'm hoping maybe it's the belt tensioners like I've read about because it's less expensive of a repair. Anyone have any ideas? Thanks a lot