1978sl timing chain

[denisp]

I have read and watched multiple versions of how to replace a timing chain on my 450sl. I have finally gained the courage to open up the motor. What I found is the Left cam shaft has a lob flattened #7 UGH a problem but repairable. As I understand, to determine the stretch of the chain. I need to align the right cam marks and look at the timing marks. Ok easy enough. The question I have is shouldn't the left cam, rotor and the right cam align also? If I place #1 at TDC the rotor will point to the mark on the base, the left cam aligns and the timing mark are close to 0, however the right cam is almost 180 off. If I align the right cam marks the rotor is 180 off I can't see the left cam marks and the timing marks are almost 20 degrees retarded.