1974 2.7 distributor vacuum advance

[csollows1]

Hi, I have a 71 911 E retrofitted with a later 74' 2.7 -- the car came to me with no vacuum advance line (although the distributor has a port for it) Can someone help me ? I have cold popping and popping between shifts that I think may be attributed to no advance/retard. I would like to know if I can tap in someplace to get vacuum or what the proper setup for the advance system should be. Thanks, Clyde

[john walker's workshop]

probably a retard, and that's why it's not hooked up. put a hose on it and suck when the engine is running. if the idle drops, it's a retard, and vice versa.

[csollows1]

Thanks !!! it is a retard, idle goes down when vacuum is applied.
So, the question is do I need it connected someplace to stop the popping or is the popping unrelated ?

[Jim Richards]

Could it be the vacuum line #25 going to the thermo valve (#26/1 via the tee #21) in the figure below? I'm just guessing, and should probably stick to MFI.

[kach22i]

The two line spouts on the back of my airbox are capped with rubber nipples.

The spout in the UFO looking advance hanging off the distributor also has a rubber nipple cap on it.

The car seems to be running fine for the most part.

Other posts says this is common and leave it be.

Could your ignition timing be off? I think this is the only time when you want to uncap the advance on the distributor.

[john walker's workshop]

stock muffler? all engines burble somewhat off throttle, like going down hill in gear, throttle closed. aftermarket mufflers just make you more aware of it.

[kach22i]

Originally Posted by csollows1

I have cold popping and popping between shifts

I've re-read the thread.

I've been running a little rich for six years (better than too lean). I've had to increase my spark plug gap just a little to make a popping between shifts to go away. This is harder on your coil though.

Do a search on the topic.