Timing Advancer Restoration

Bosch Timing Advancer for Heinkel Car Engine

This little item controls the timing advance on the Heinkel engine. I don’t know what to call it; a timing governor, and timing advancer? I’ll just call it a timing advancer for now.

I had a few of these floating around for my parts engine. They were all pretty rusty looking, and were perfect candidates for restoration.

Rusty Bosch Advancer (top) and Siba (I think) bottom

Here’s how I think they work:

The little “arms” are weights on pivots, which are held close to the cam by a set of springs. As the engine turns faster these arms pop out through centrifugal force, which rotate the cam in the middle to advance the timing of the engine.

Here’s how I restored it:

I dropped the whole thing in my electrolysis setup (you can read about electrolysis here). A few hours later most of the junk was off of it. I used a Dremel buff to remove most of the dirt and rust, then stuck it back in the electrolysis vat for a few hours.

Bosch Advancer (bottom) after Electrolysis

After the last electrolysis session everything was loose enough so that I could actually take it apart. The arm weights are held on with clips that were easy enough to pull off. The cam is held on with a clip and a couple of spacers. All three of these have to be removed in order to pull all of the parts off of the base plate.

Timing Advancer Parts 

An extremely thin insulating washer is under each arm. It seems less important that they are insulating washers than that they reduce friction by keeping the weights from scraping on the base plate. These little washers are not obtainable from the club or from the hardware store, so I had to make my own (since mine were missing).

I received a flash drive in a little case at a trade show. The plastic cover of the case was a nice thickness for what I wanted, so I made a couple of washers from that.

I decided to replace the springs as well. Bosch springs are available from the German Club. If you have a Siba setup, the advance and the springs are different. The spring tension affects the timing, so if your Siba springs are missing or rusty you may have to buy a used advancer or see if you can find springs elsewhere.

The final piece to evaluate is the cam itself. It should be smooth and not pitted. Since mine was rusty and I removed the rust, I had a rough surface remaining. A smooth surface is important so you don’t prematurely wear out the piece on the points that rubs against the cam.  

I lightly sanded mine with a scotch pad just in case there were any edges that could contribute to wearing off the plastic points piece. I'll keep an eye on it. The alternative I considered was  to fill the gabs with epoxy. 

That's it. Hard to believe such a little piece could play such an important role in the performance of your engine.