For what purpose these intake manifolds are different?

[Aram]

I have the two kinds of manifolds, the carburetor I'm adapting comes from a classic Lada. The Lada manifold has one single slot in the carburetor seat; the manifold that came with the engine is the kind with two interconnecting "holes":

 

The first top pictures is the manifold that came with the engine, the picture below is the other manifold resembling very much a Lada's (from which I will use the carburetor).

 

My guess is that in the "holes" manifold, the top hole which has an insert ring, provides something like a pool of gas, to help the engine crank perhaps in cold Czech winters When I teared the engine into parts, I could see a puddle of gas there. To start this engine (which already had a Lada carburetor) I had always to kick the gas pedal a few times before running the starter.

 

The second manifold does not comes with the vacuum port for the brakes, but that's something I can add.

 

So my question is a bit complex, hopefully someone with experience could guide me:

 

Is there any real benefit or not (from any angle: consumption, performance, etc) by installing the second manifold? Besides just resembling the Lada's carburetor seat...

 

[KenONeill]

@Aram I presume the Lada is a 1200 (or 1300, 1500 or 1600)? (aka a VAZ-2101 (1200) or 2103 (1500)). If so, a quick Google showed that it has an 8 port head where the Skoda has a 5 port. Or wasn't that the question?

 

I honestly can't see any benefit to the one manifold over the other; what I would say is that your description suggests that the automatic choke actuation wasn't properly set up when you bought the car though.

Edited 19 April, 2017 by KenONeill

[Favorit Fan]

Im not certain but the twin hole manifold might be shaped to better suit a twin choke carburettor: the inserted tube might have been fitted as a shield to protect the second choke from gaining too much vacuum; as both chokes are able to supply extra fuel in response to higher suction levels when the engine is under load. While this extra fuel is necessary to enable the engine to stay running and keep doing engine braking when running downhill, separating the chokes in terms of vacuum helps to allow the second choke to have a greater effect, and makes it easier to fine tune the fuel delivery quantities so that it doesn't cause the engine to run overly rich all the time.

[MotorsportFinland]

The manifold with insert ring is most likely designed to help vacuum operated secondary butterfly work better. Skodas have Jikov EDSR and SEDR type carburettors, and both of them use vacuum operation, however in Wartburgs Jikovs are SEDR -type but mechanically operated secondary butterfly. Wartburg manifolds are simply oval shaped.

There are also Skoda manifolds with steel plates, hole shaped with kind of a star for secondary choke (similar shape that is used in pastry bags/piping bags for baking purposes). I think that perforated hole is designed to work similarly in conjunction with vacuum operation?