Timing and Vacuum line disconnect

[tonyduc]

All
Regarding timing my 77 911S, the manual says for US cars (other than Calif) to disconnect vacuum line (0 +/- 2 at TDC @ 950rpm +/- 50), Haynes additionally mentions to plug the vacuum line. However, when I disconnect the line from the distributor the engine races (whether or not the vacuum line is plugged) as soon as I reconnect the line it returns to normal idle whether the vacuum line is plugged or not. I am using one of those gas line plier type clamps to plug the line. Am I supposed to also plug the distributor?

Thanks
Tony

[47silver]

Many posts on this. Some say disconnect and plug the vacuum line and set timing at 6000 rpm to 3x degrees.
Then adjust idle wiith the large slotted idle screw.
That is what i do on my 75

[6cylboxer]

Tonyduc: I also have a 77 and the instructions i follow are on the decal that is placed on the fan housing - States: Ignition timing TDC ±2° at idle speed (vacuum line connected)

[Flat6pac]

The vacuum line on a 2.7 is a vacuum retard line, works only at idle when the butterfly is closed
It backs the ignition to ATDC for ignition burn time.
The engine races when disconnected because the distributor is advancing.
Bruce

[911obgyn]

Golf tee works great at plugging vacuum lines