Carburetor swap weber 38

E3AV

E3AV

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Hi!
My E3 2800 currently has a solex 4A1 4-barrel carburetor setup installed by some previous owner.
I’m no carb expert but my plan is to convert back to a dual carburetor setup using Webers. Giving the engine bay a more stock appearance with the original air filter housing in place.
I have started sourcing parts and so far only got the intake manifolds. Got a very good deal on a pair of used weber 38DGES carbs and they are on the way.
Also ordered new air filter housing adapters.

I have seen in 02 forums that it is beneficial or even nessesary to modify the opening in the intake manifolds when installing 38’s.
Does this apply to the m30 manifolds as well?
The 2 holes in the manifolds have different sizes 40 and 36mm.
Will this affect tuning the carburetors in any way? Restrict air flow or making som turbulence?
I have no problem with making the holes the same size or even making one large oval hole if its any point in doing so.
I know there are spacer gaskets available. Will these rectify any issues?

Finally, any suggestions for a starting point regarding jetting?
The Weber seller was unsure of the current setup.
 
Done lots of 2002's and always cut the manifold opening to one hole matching the gasket. Much better flow. double check the cooling chamber gasket on the bottom side of the manifold as well as a plug to that chamber inside the manifold for any signs of leakage

I have an original air cleaner housing that I have restored that would look great with your carbs for sale. PM me for more info.

Thanks, Rick







m
 
Ok. Then i will grab my die grinder and get to work.
Oh.. yes forgot. I also have the air filter housing almost ready. Sandblasted and epoxy primed ready for paint. Black or gray.
 
Yes you'll have to match those holes because 38's aren't progressive. Depending on the previous use of the carbs, you may be in for some jetting changes too.
 
bmw2800cs said:
More agressive Cam too? I'm considering 38's with a Cam upgrade. Let me know how it goes :)
Click to expand...
Yes I may do that.
Only other modification so far is stainless steel exhaust with headers.
Stevehose said:
Yes you'll have to match those holes because 38's aren't progressive. Depending on the previous use of the carbs, you may be in for some jetting changes too.
Click to expand...
Yes I’m sure it will be some trial and error.
Would the standard jetting for the 38s be a good starting point? I guess I’ll have to wait and see whats in them anyways before trying anything.
I found this to be the standard settings:
Choke: 27
Aux venturi: 4
Main jet: 145
Idle jet: 45
Emulsion tube: F50
Air corrector: 185
Pump jet: 70
Back bleed: 30
Needle valve: 250
 
I found this thread very helpful when doing my conversion.

Explain the "Jim Rowe Power Valve" modification, please

Because it’s downstream of the carburetor or injectors/manifold, it’s already mixed by the time it’s ignited. Afr gauges read oxygen and convert to afr so they are not 100% accurate. Timing does not affect the mixture of fuel and air, that’s impossible. So tuning afr with timing changes will...
e9coupe.com e9coupe.com
 
E3AV said:
Yes I may do that.
Only other modification so far is stainless steel exhaust with headers.

Yes I’m sure it will be some trial and error.
Would the standard jetting for the 38s be a good starting point? I guess I’ll have to wait and see whats in them anyways before trying anything.
I found this to be the standard settings:
Choke: 27
Aux venturi: 4
Main jet: 145
Idle jet: 45
Emulsion tube: F50
Air corrector: 185
Pump jet: 70
Back bleed: 30
Needle valve: 250
Click to expand...
Thats a good starting point
 
Is there any point in using spacer gaskets if I make modifications to the manifolds?
Heat insulation?
There are different height/thickness available. I read somewhere there could be some clearance issue between the hood and air filter housing using to thick spacers. True?
 
E3AV said:
Hi!
My E3 2800 currently has a solex 4A1 4-barrel carburetor setup installed by some previous owner.
I’m no carb expert but my plan is to convert back to a dual carburetor setup using Webers. Giving the engine bay a more stock appearance with the original air filter housing in place.
I have started sourcing parts and so far only got the intake manifolds. Got a very good deal on a pair of used weber 38DGES carbs and they are on the way.
Also ordered new air filter housing adapters.

I have seen in 02 forums that it is beneficial or even nessesary to modify the opening in the intake manifolds when installing 38’s.
Does this apply to the m30 manifolds as well?
The 2 holes in the manifolds have different sizes 40 and 36mm.
Will this affect tuning the carburetors in any way? Restrict air flow or making som turbulence?
I have no problem with making the holes the same size or even making one large oval hole if its any point in doing so.
I know there are spacer gaskets available. Will these rectify any issues?

Finally, any suggestions for a starting point regarding jetting?
The Weber seller was unsure of the current setup.
Click to expand...
I went the other way - ditched the Webers for a Quadrajet. It works like a trained pig. Here are some pics and a description.

D-jet? J-Jett? L-jet? How about Q-jet?

I've had this euro 4-bbl manifold for several years and I finally decided to put it to use. It had a Solex 4A1 on it when I got it, but it looked kinda funky. I noticed that the bores matched a Quadrajet very closely so I decided to go that route. I have a dozen or so of them so I decided on...
e9coupe.com e9coupe.com
 
Al Taylor (who sells parts here as Bavman from time to time) had one of those on an E3 he was racing a couple of years ago. He really liked it.
 
As for the Solex 4A1 installed in my car, it seems to work ok. But I have little knowledge of it and I have heard that the 4A1 can be difficult to service and tune.
My carb also seems to be missing 2 vacuum operated devices. I don’t know the importance of having them. One is some sort of anti stall device and the other some sort of damper.
The anti stall was removed because of clearance issues with the brake booster I think.
I’ve read in Mercedes forums that tinkering with the 4A1 can lead to even more problems than you started of with and is best left to experts to deal with.

Weber knowledge is plentiful and spare parts are easy available and inexpensive.
 
I recall an available conversion kit to install Weber 4 barrel in place of 4A for Euro models, similar to this M20 adapter.

1724878747745.png
1724879550535.png

May have used the Weber/Edelbrock 4 barrel commonly available for marine engines, possibly for BMW marine 6 cylinder.
 
On your first picture I think there is a kit to make a single Weber 38 fit the 4 barrel manifold.
The DGAS 38 was used on Ford Essex V6 3.0L engines so it probably would have worked on my 2.8L as well.

Anyways.. I’m converting back to two separate manifolds and the two weber 38’s are almost ready to go on.

I have modified the manifold openings to fit the Webers nicely. Just waiting for spacer gaskets to arrive.

The Webers looked reasonabely well when I got them. Just some minor cleaning.
Jetting seems to be standard.

I got one carb with brass float and one with plastic. Is this ideal?

And since I’m converting to electric choke, what to do with the coolant line used with the water choke? Just plug the inlet/outlet at the manifold and engine?
 
as long as your floats act float (test them) there’s no concern about different materials. I converted to electric choke and plugged the manifold with a rubber cap held in place with a small clamp.
 
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