what the hell is this noise?
 

I just got my '79 911sc back from a full paint job with bodywork and it has developed a rather troubling engine noise. I think I know what valves sound like, and I don't believe these are its cause. It is a marbley, inconsistent rattling emanating from the bottom side of the engine that seems to occur primarily at low idle, though it simply may be more apparent in the relative quiet of 800 rpms. There isn't much more to it than that. Tech books suggest timing chain issues or cam bearings. To me it sounds a lot like the bent pushrod issue I dealt with in a 1967 Corvair. (The Corvair ran $400 for a fix; God only knows for a P-car.) Does anyone have a clue as to the source of my pain?? Any input would be greatly appreciated. I'm considering simply turning up the idle and keeping my fingers crossed.:)

Well it certainly won't be push rods :) I vote for tensioners.

sounds like a collapsed cam timing chain tensioner. What kind you got? Carrera updated pressure fed? 930 sealed? do you have safety collars?

Intermediate shaft backlash? Does it go away if the idle increases?