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Hello!

After restoration, I am currently putting together an e21 315 with a 1.8 m10 carburetor engine.
Maybe someone can help solve a couple of questions:

1. Does this carburetor system does not have a fuel return pipe to the fuel tank at all? It wasn't there in the beginning, before the car was restored.

2. What is the function of the following outlets in the carburetor (in picture ''3'' and ''4'')?
Photographed before disassembly (the car was running fine, but I don't want to leave such a solution.


3. What is the outlet from the valve cover for? In the picture ''2''?


4. What is the outlet from the intake manifold ''1'' for?


Thanks in advance!

It's in German, but you might find this useful https://www.ruddies-berlin.de/se1B2.htm

Or this one https://www.ruddies-berlin.de/se2B4Serv.htm

Number 2 is connected to the crankcase ventilation. Some gases flow by the piston rings and create over pressure in the engine, this needs to be vented. The little opening probably is for a vacuum connection so you 'help' to suck out the gases, I'd connect it to 3.

Around the throttle valve there are different vacuums. Before the throttle there is a little bit, after the throttle, when it is closed, there is a lot of vacuum. At full throttle there is less vacuum. To negate this change in engine load, the ignition timing needs to be changed as well. I would connect number 1 to the distributor to give vacuum to the distributor for vacuum advance.

Before the air filter in the tubing, there is another vacuum pot. I would connect 4 to that one.


What do the others think?