My M40 316i has since the service I gave it 300 odd miles ago, started to sound very tappety.
I fix this today and it took less than 45 mins.
I removed the cam cover and the plastic cover over the camshaft, then removed the 8mm bolt at each end of the oil spray bar and the 13mm banjo bolt from the middle.
There is 8 small holes in the spray bar which allows oil to be sprayed directly onto the cam lobes, these holes on mine were blocked so I pushed a piece of wire from my wire brush through them each.
Next I cleared it through with aid of an aircompressor and got some sludgey oily yogart residue out.
Re-assemabled it and started the motor up and ran it till it was warmed and the tappety noise has gone.