I don't have a diagram to show you but if your car is US spec it connects to a tube that runs through the firewall, along the floor and in to the trunk. It sends gasoline vapors from the fuel tank back into the engine in order to save the planet.
There are four variations of the breather fitting that bolts to the cam cover.
1: It has the main breather hose and no small extra hose.
2:It has the main breather hose with one small hose at 90 degrees to the inlet manifold. That goes under to the front of the inlet manifold as in the diagram I provided.
3: It has the main breather hose with a small hose that runs parallel to the intake manifold the goes to the canister at the rear as part of a fuel vapor recovery.
4:Main breather hose with two small hoses. One at 90 degrees going to the front of the manifold, the second running parallel to the intake manifold going to the rear fuel canister.
The fitting the OP has was intended to go to the front of the inlet manifold as shown in the diagram I provided.
On early cars with the remote air cleaner the 90 degree small hose can also run straight back to the air box.
Alfaparticle if you are talking about a SPICA car I simply wouldn't know but would like to see a diagram so I can understand.
First two pictures are of inlet manifolds. One with the fitting, one without. The rest are variations of the breather that bolts to the cam cover. I think its pretty straight forward which ones match each other. I have no idea which car is supposed to have which ones with regard to originality. I'm lucky if I can remember my own phone number so I'll leave that sort of detail to someone else.
I have a '66 1600 GTV that I am sorting out wrong parts that the prior owner put on from a 1750 (Last picture! and yes, the seats are 1750 seats! but I am keeping them). I am replacing the intake manifold seen in picture #1 with a screw in manifold with 40mm/32mm port size (carb side/engine...
Thanks, fellas. It looks like I can go ahead and plug the small fitting (or swap out to an assembly without the extra fitting), since there doesn't appear to be a corresponding fitting on the intake manifold.
I have one of the Alfaholics catch cans that I need to install. Want to do their pedal box first so I can see where I have room. Until then, I have a road draft tube that exits on the bottom of the engine compartment.