500 SE engine noise when cold

I have engine noise (tappets and rockers) on start up when the temperature is below 7 degrees Celsius outside, which is occasionally accompanied by a muted knock at the front of the engine. My car has covered 122000 miles.

Is it likely that new hydraulic tappets and rockers will quiet the top and that timing chain wear and stretch may be causing the knock? the oil pressure is good and only drops to 2.5 bar at idle when the car is very hot after a long run, but immediately goes to 3 bar from 800 rpm onwards. Are there any workshop manuals around that will cover the m117 engine fitted in my car?

Thanking you all in anticipation.

Ian.

[Benzmac]

I would think that this noise is the timing chain tensioner not pumping up quickly enough. You should have the timing chain and sprockets checked and the tensioner replaced at least.