How to determine TDC ?

[bpossel]

I know that there are many posts on this subject, but I am struggling trying to determine TDC on my car.  I am in the process of re-installing the IP after having it rebuilt by Hans at H&R.

Here is where I am with this currently.....

I have rotated the engine manually using the 27mm socket.  I can see the cam lobes on #1 at the 10 & 2 o'clock positions by looking through the oil filler hole.  The rotor is pointing directly at the #1 spark plug position that I marked before I removed the rotor cap.  The rotor also lines up with the factory notch that is on the distributor.  Here is what puzzles me....  the timing mark on the flywheel is sitting on 30 degrees BTDC.  Why?  Should'nt this now be sitting on zero???

Help!  Thank you!
Bob


bpossel
Memphis, TN.
1971 280SL
1997 E320

[ja17]

Hello Bob,
Later W113 engines have two scales on the vibration dampner be careful that you are using the correct one. Mercedes changed the pointer design in later cars and just inscribed a second scale on the dampner as a result.
First turn the engine clockwise (facing it from the front of the car) until it reaches "0" sometimes "0T". If you have two scales use second scale for later engines (closest to block). After finding TDC turn the engine an additional  20 deg. clockwise (ATDC) before installing pump.

You can carefully stick something in the spark plug hole of number one cylinder to double check yourself. The no. one piston will be all the way at the top when at TDC. Be sure not to have anything in the spark plug hole while your turning the engine or it will jamb or break.

Joe Alexander
Blacklick, Ohio

[bpossel]

Thanks Joe (and Mary),

I ended up taking off the valve cover to ensure that I was at TDC.  Lined up the notch on the top sprocket "washer" with the mark on the cam shaft.  This also lined up the timing mark to zero degrees, and the rotor was also lined up on the factory notch on the distributor.  I then rotated a bit further until I hit 20 degrees ATDC.  Ensured that the IP notches were lined up and slid the IP onto the block.  

If anyone needs help on replacing their IP, please email me.

Thanks again!
Bob

bpossel
Memphis, TN.
1971 280SL
1997 E320