Original Carburetor replacement on original engine and injection engine?

[tom]

Hello, Tom from germany speaking/Asking basically 2 Questions:

1) Has there anyone replaced the original carburetors on a 3.0 CS (1972) by some different carbs but with untouched Engineblock/head/crankshaft/pistons...?

Is there a substitution carboretor kit existing which works after installing / adjustment without modifying anything else?
(i´m not seeking for more power - if there will be 5,10 PS more - fine, if same as old fine too)
Head# 1250019 (9) Block: (i think its xx 446)

2) When having a different engine (Head/ Engineblock of the 3.0SI injection e3 e9) which caburetor set would work here without touching Engineblock/head/crankshaft/pistons? (only removing the injection itake manifold and replace by Carbs) maybe just mod the fuel pump external instead the mechanical attahced to 019 head
the head number is 1277358 + Block 753L A 12 01

Does anybody have done this "modification" / exchange and what are the exact Products (+ numbers) used?
(What did maybe not work -> experiences highly appreciated)
Thank you, Tom

 

[jmackro]

If I understand your question #1 correctly, the answer is "yes". Many e3/e9 owners have exchanged their original Zenith carburetors for Weber 32/36 DGV series carburetors. The Webers will bolt onto the original BMW carburetor manifold. Note that Weber 32/36's are available in three versions: manual (e.g., cable) (DGV), coolant (DGAV) or electrically (DGEV) -operated chokes. Some fiddling with the throttle linkage is required when switching from Zeniths to Webers to prevent over-centering at maximum throttle.

The Webers won't give you any additional power and many owners feel that a properly tuned Zeniths are better for fuel mileage and smooth operation.

 

[Ohmess]

Also, Carl Nelson used to recommend the Weber 38/38 downdraft carburetors as an alternative to the 32/36s.

I had 32/36 DGAVs on my car when I bought it. They do not require any modifications to the engine, but you need a pair of mounting blocks to mount the carbs to the intake manifold and a pair of air filter adapters in order to attach the stock air cleaner. And, of course, you will need to modify your linkage. I believe a pair of 38/38s would require these same changes.

If you are starting with an engine that had fuel injection, you need a fuel pump that is appropriate for the carburetors. I have Weber sidedrafts, but my fuel pump would be appropriate for downdrafts as well. https://e9coupe.com/forum/threads/adding-a-electric-fuel-pump-suggestions.42221/post-369474

 

[Mike Goble]

I went a step further and found a single four-barrel manifold from a euro model M30 and adapted a Rochester Quadra-jet to it for my M30B35 motor. Much simpler to work with than two carbs. No synchronizing, no linkage adjustment issues, great throttle response, readily available performance parts and unique in its application.

 

[ScottAndrews]

You should be aware of a few key points. The carbureted heads have a provision for a mechanically driven fuel pump. So if you are converting a csi head to carbs you will need an electric fuel pump. Other than that the csi and carb heads are the same. You need to be careful if changing to a different head (B34/35, etc) since the combustion chambers are not all the same. You will need the appropriate intake manifold and throttle linkage for whatever carbs you use. I am adapting an M90 engine to use triple Weber side drafts, and that requires a unique manifold and linkage. The air filters are substantially different between CSi and down draft carbs. Depending on the combination of head and manifold you may need to do some porting, since the size and shape of the intake ports is different with different heads. Not really an issue if you are using a stock 3.9 head

 

[ScottAndrews]

I went a step further and found a single four-barrel manifold from a euro model M30 and adapted a Rochester Quadra-jet to it for my M30B35 motor. Much simpler to work with than two carbs. No synchronizing, no linkage adjustment issues, great throttle response, readily available performance parts and unique in its application.

View attachment 219704

That’s a unique solution!!