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I'm helping a friend with a 1971 Berlina 1750. At some point the engine was changed to a 2000. We have rebuilt the carbs (40DCOE32) and assume they came off the 1750, do they require different jets for the 2000?
 

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I'm helping a friend with a 1971 Berlina 1750. At some point the engine was changed to a 2000. We have rebuilt the carbs (40DCOE32) and assume they came off the 1750, do they require different jets for the 2000?
Hi Pietro. Some publications indicate that 1750 and 2000 are jetted the same for 40 DCOE 32's. Although I have I believe seen other info indicating some differences. You can search jetting for 2 ltr carbs in Carb forum to find some discussion that might be of interest.

Regards

Ken
 

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Here you go, One of the publications I was referring to.

ken

1606706
 

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My understanding of Weber jetting (and admittedly others know much more than I do) is that engines are very sensitive to jet, air corrector and emulsion tube sizing. Changing displacement would certainly trigger the need to change these components; so would changing altitude, camshafts, compression, ....

This isn't to say that your 2000 won't run with carbs set for a 1750. Just that it will run better / more efficiently if you fine-tune the jet sizing.

Why don't you post the part numbers on the jets, air correctors and emulsion tubes currently installed, as well as tell us a little about the engine they're going into, and get some opinions about how to re-jet them. But the best way to fine tune this is with an oxygen sensor and dyno, or by recording the O2 levels while driving under varying conditions.
 

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I would be surprised if the optimum 1800 jetting were different from 2000. If there is any change required then it may be to the Air correctors. But provided that the venturis are the same and you are not at higher elevation then stock jetting is likely to work fine.
 

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Discussion Starter #7
Hi Pietro. Some publications indicate that 1750 and 2000 are jetted the same for 40 DCOE 32's. Although I have I believe seen other info indicating some differences. You can search jetting for 2 ltr carbs in Carb forum to find some discussion that might be of interest.

Regards

Ken
Thank you..........
 

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My understanding of Weber jetting (and admittedly others know much more than I do) is that engines are very sensitive to jet, air corrector and emulsion tube sizing. Changing displacement would certainly trigger the need to change these components; so would changing altitude, camshafts, compression, ....

This isn't to say that your 2000 won't run with carbs set for a 1750. Just that it will run better / more efficiently if you fine-tune the jet sizing.

Why don't you post the part numbers on the jets, air correctors and emulsion tubes currently installed, as well as tell us a little about the engine they're going into, and get some opinions about how to re-jet them. But the best way to fine tune this is with an oxygen sensor and dyno, or by recording the O2 levels while driving under varying conditions.
Thanks for the info......
 

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2000 will not run clean on unchanged 1750´s jetting as DCOE32´s never have been factory used on 2000´s.
That´s not only a theoretical explanation but based on own experience.
 

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Hi,
italian berlinas have main jet 125 for 1750cc and 130 for 2000cc.
There are two type for 40DCOE32 (in Italy), idle screws are different
I don't remember if the emulsion tubes are the same.
Now I can't verify.
Bye
 

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Hi,
italian berlinas have main jet 125 for 1750cc and 130 for 2000cc.
There are two type for 40DCOE32 (in Italy), idle screws are different
I don't remember if the emulsion tubes are the same.
Now I can't verify.
Bye
The 2 types of DCOE32 are early and late type for 1750 only. Not for 2000. Do differ in more than main jet!
 

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Hi all,

As hunttheshunt mentioned before, I also thought that the 105 Alfa 2000 originally, never came with Weber carbs but used or the Dellorto DHLA40 or the Solex 40DDH. There were some ( few) different settings between 1750 and 2000 on those carbs.
Btw my 2000 GT that I had 30 years ago had the Dellortos.

Now I found out that Weber did list at least some carbs for these 2L cars but I’m still not convinced that they were mounted originally by Alfa.

The picture from the 1986 Weber catalog showing the carb #s for the 105 Alfa 2000 cc.

If you can find an original of these carbs, you’ll know what was the Weber settings for the 2 liter.

FWIW, the Weber 40 DCOE 72-73 on the listing from Centerline were, according to that Weber catalog, for the 1800 Alfetta’s, not for the twoliter 105.

Always open for other thoughts,
Rgds,

Thierry
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I'm helping a friend with a 1971 Berlina 1750. At some point the engine was changed to a 2000. We have rebuilt the carbs (40DCOE32) and assume they came off the 1750, do they require different jets for the 2000?
Your 2000 will run fine with the jetting for the 1750. But, agree on the "fine tuning" advice. More importantly, are the mounts and the balance. If the mounts have cracks, replace them. No amount of fine tuning will make up for air leaks. Balance is equally important. If you don't have access to four vacuum gauges or a manometer then borrow one/some. Your first task is to make sure the front and rear carburetors operate synchronously. The screw in the center between the carburetors controls this and a manometer or four vacuum gauges, each attached to one throat of the carburetors, will immediately show if you have them synchronized. Vacuum reading should be between 15-18 Hg across the board. Its OK if they are 1Hg off. That's the tolerance. More than that and you'll have work to do.
 

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I've used Webers on several 2L motors with US cams, Euro cams, C&B cams and two different pairs of RJ race cams. It could be that a 2L will run slightly better with different jetting than for 1750 but you will be hard pressed to tell the difference. I agree with Paul that air leaks will prevent any jetting from working well but I disagree about manometers. You can balance the carbs perfectly by removing the screwed plugs above the progression holes and adjusting the synch screw until the edge s of the throttle plates are in the same position on both carbs.
 

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Well, I may be the outlier here with my setup, and my original 2.0L engine has not been "breathed" on, but for the last 27 years I've run my '73 2L ( I bought it new in January 1974, then with Spica), w/Weber 40DCOE32s, Euro intake manifold and airbox, MSD 6200 (installed in 1983) multi-spark box, OEM '73 Spica cams and OEM '73 pistons, with a conservative setup for maximum around town torque and driveability. The throttle response is very smooth, with no flat spots. Here is my setup:

Carbs - Weber 40DCOE32
Settings
Chokes- 30mm
Emulsion tubes - F16
Main jets - 115
Idle jets - 50F8
Air correction jets - 200
Accelerator pump jets - 35
Auxiliary venturi - 4.5
Accelerator pump bypass - 55

I know the chokes are smaller than what most people recommend for a 2L, but it has worked for me for quite a long time. If you're interested in getting the most high RPM power out of your 2.0L engine, you'd use a different setup. However, for around town and periodic "twisty parts" driving it is my humble opinion that a setup that gives you more low RPM torque will be more satisfying for most folks. Also, in my experience, once you get the Webers set they'll stay tuned for quite a long time. In fact, my Webers have been untouched since 1992!

Bob J.
 
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