TDC

Warren Hall mentioned in a previous post that it is always important to have the engine at TDC on cylinder #1 whenever you pull the distributor. Why is this so? Can't you just mark it before you pull it and install it according to the mark?

There are several good reasons, or justifications for using #1 TDC as your point of reference when the distributor is out:

1. There is already a mark--a notch on the distributor body, so no mark that can be wiped off will have to be relied upon!

2. If the engine needs to be turned over for any reason, you always have the pulley TDC mark, and #1 intake and exhaust valves to re-time the distributor by -- no matter how far you get away from where it was when you removed the distributor!

3. There is no reason to do things on a whim when dealing with a 911 ... if there is a 'standard' way of doing something, there are fewer chances of a mistake causing you grief ... or panic! Kurt could probably elaborate on the grief part.

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Warren Hall
1973 911S Targa

Of course you can mark it and replace it just as it came out.
Trouble is that it is easy to get the distributor drive one tooth out of place and then have the hassle of setting the timing from square one.
The gear at the end of the rotor drive is not straight cut and you will see the rotor rotate as the gear engages when you push the rotor in place.
That apart, you are flying blind on the timing if you make a mistake and then start to wonder where it is set.
Amateurs, as I am,need to keep it simple. In this case, simple is putting it at TDC before pulling it.
To eliminate any confusion on tdc marks, daub the mark with white paint so that with the car in gear, you can put a socket on the crank nut, push on the belt and bring it to tdc quite easily.
Ned Monaghan