It's not difficult to install the woodruff key...

After removing the cam sprocket bolt, chain guide and the tensioner bolt/plug, I used a rubber mallet to tap the sprocket off the end of the cam. There's just enough room in the chain gallery to allow the sprocket to come off the end of the camshaft.

Just make sure you know which way to orient the key...

There's enough slack in the chain to allow you to place the sprocket back on the end of the camshaft, align it with the keyway and tap it home with your mallet.

Word of warning:
Drape everything and stuff extra rags in the chain gallery. You don't want to be loosing anything down in there!!! SWMBO walked out when I was in the big middle of the procedure, spotted all that draping and claimed that I was taking Benz mechanicing a bit too far.

I ran out of time that particular day or I would have checked and adjusted the IP timing as well.

Any way you cut it (stealership/wholesale or aftermarket), an armload of woodruff keys is a whole lot cheaper than a cam chain. IMHO, it's a valid fix too. MBZ wouldn't have a procedure for it if it didn't work.

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Never a dull moment at Berry Hill Farm.