W108 adventures
 

I bought my 280SE four years ago knowing nothing about classic Mercedes. Thanks in part to this forum (many thanks to the members willing to share their knowledge) and my MB shop manual, I think I finally have it running well. I made the Pertronics conversion but found so many more things wrong. This included a locked up mechanical advance in the distributor, and a leaking distributor vacuum actuator.

I then started looking into the AAV and found it was not even closing half way. A wrench on the hosed proved it would make a difference when functioning as intended. I looked for a replacement but decided on trying the Tomguy bulb squeeze instead. What the hell, I own a vice. It worked, and made a difference when starting the beast. However, it does not completely close off. I can still hear air bypassing so should it close 100%? Vice it again?

Second question. I recently read a reply from Graham that he sets his timing at 6 degrees BTDC with vacuum connected. I set mine at 6 degrees with the vacuum line removed and plugged. Did I read this correctly? Apologies for the long post.

These should close off 100%. I like to remove them and boil them in a pot of water. Then, using a pair of pliers, I pick them up, slip on the hose and blow through the hose. If I can blow at all I know it will not work as planned.

But if only a tiny bit of air gets through then, yeah, they will work OK. Or at least until you can find a good one.

The vice squeeze thing will only take you so far. When these are new the bulb is smooth. When they are rebuilt by the factory you will see four indentions running up the side of the bulb. This is where the rebuilders put the squeeze on it.

The early ones can be rebuilt but it is a major process. There are instructions on line where others have done it. The later models cannot be rebuilt, or at least I have never heard of anyone doing it.

You can also boil them and hold a strong small flashlight up to one of the holds and look through them. Do this at night and have someone flip off the lights in the room. Then hold the bolted valve up, holding the hot valve with the pliers, and shine the light through one side and look into the other. If you see any light they are leaking. You should see total darkness.

This prevents you from having to blow through it. Even with the hose attached and blowing through it they are still hot and rather close to your face.

the most important timing angle is measured at 3000 rpm vacuum disconnected (simulating full load) because that's when if you have wrong timing you can do damage, don't worry about idle timing.

I think it should be between 18-22 degrees (3k vac discon.) for a 1972 us model M117 engine

page 2 of this pdf has more info:

https://www.startekinfo.com/StarTek/outside/11883/PROGRAM/Engine/107/M117_45/075-500.pdf