I’m confused on setting TDC while replacing the chain rails on my ’87 420SEL.
Before replacing anything I turned the engine to TDC by aligning the cam shaft gear scribe with the mark on the passenger’s side cam tower. There was 15 degrees of chain stretch.
After replacing the rails and tensioner on the passengers side there was 11 degrees of stretch. Now I’m moving over to the driver’s side to change the rails. I opened up the distributor to begin removing it. I was surprised to see that the rotor arm is almost 180 degrees off, exactly opposite, of the scribe mark on the distributor housing even thought the cam shaft marks were still aligned at TDC. Just to experiment, I turned the engine until the rotor lined up to the scribed mark on the distributor housing. Of course, now the cam shaft mark is not lined up to the cam tower, and the pointer is showing 40 degrees on the harmonic damper. The manual says the distributor rotor is supposed to be aligned with the scribe mark and the engine should be at TDC before the distributor is removed.
What am I missing here? BTW, I will be replacing the timing chain after I chain the rails.

TDC usually refers to being at Top Dead center on a compression stroke. #1 piston all the way up and both valves closed (cam lobes pointing away from the valves). Sounds to me like you weren't on the compression stroke.

__________________
Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

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