Figured I would add some info to the archives as I’ve recently purchased a true dream car of mine! A C6.5 S6, White on Carbon interior.
As an Engineer by trade, I tend to search for challenging/fun/rewarding projects…
So when an “Inoperable S6” ad popped up, I jumped. The seller only mentioned his local mechanic inspected the car after the engine lost power and concluded a valve had bent (unknown location).
Regardless of the lack of info, the car was well maintained with an even 100k miles on the clock. I made an offer and got to work right away.
Ok, not too bad so far. Let’s keep going…
But first… much better! The little simple things matter in projects such as 
Back to real work…
After a quick VAG scan I found multiple cam sensor open circuits. This immediately added to my concerns of timing related failure, closer inspection shows both bank lower cam sensors left unplugged. Assuming mechanic who inspected last was doing me a favor 
Onward!
Oh ya, found a surprise out back… Milltek!
Also found another surprise whilst removing the intake manifold!!
I cleaned the bits out of all the ports, removed the port spacers and began to inspect the extent of the carbon build up.
At this point, all inlet valves were in their correct position related to crank position… Cool!
Next step was to rotate the engine over to confirm that the valves do move correctly.
Unfortunately Cylinder 5 showed one intake valve not following engine rotation, as seen above. The right valve is fully open, while the left is still seated.
This is where I am currently at, my thought is I will find a rocker arm popped off cylinder #5 when removing valve cover.
At this point I am prepping for engine drop and RH cylinder head replacement. Unless anyone has knowledge behind rocker arm “failure” and if it is possible to re-seat a new rocker arm with the camshafts installed. I doubt it.
Thanks for the read! I’ll keep this updated
EDIT: Found this link - 2008 Audi S6 v10 misfiring( rocker popped off)
. So far I’ve noticed one of the intake valves spins freely by hand and is pushable by handforce but moves correctly in relation to the crank position. Engine will be removed at some point, biggest challenge might be that I’m doing this at a home garage without a 2-post lift. Great project and good luck with the engine!