Thanks Alex. Considering your experience I feel it is probably preferable to just wrestle through the plug change with the upper manifold in place. The driver's side is really tough; the passenger side is fairly easy.

Why did you have to take valve cover off?

Do y'all think the reason MB sets up timing marks as something other than TDC is because at the setting they have it everything is as "relaxed" as engine can get? No pressure from valve train trying to move cams in other words?

To use the cam locking tools he has.

The primary reason is to have all of the pistons slightly down in their bores. This prevents bending of the valves if a piston is fully up and cam is turned.

This step of having pistons down in their bores is also very important when installing heads / cams on most any other engine even if it is times at TDC.

Thanks for explanation.

Hey all, I am late to this party but am about to try this exact repair on my '13 E350. I had a failed tensioner on the passenger side bank, went through all the steps to replace the tensioner at 40d but still have codes being thrown so I am certain I jumped time a tooth or two.

My big unknown is once I reset the engine to 40d and verify the driver's side is in time, is it just removing the camshafts on the passenger side, set them back in the correct time, make sure everything is aligned?

If it's just the intake camshaft out of time can I just rotate that one?

Thanks in advance.