Dellorto Dual Carb issue

[Pt6295]

Hello everyone, I am the proud new owner of a 1975 124 spider. The car is in overall good shape with the exception of a carb issue. The previous owner installed dual Dellorto 40 carbs. The car idles rough and pops at all rpm's. I checked the vaccum pressure on each barrel and the readings are all over the place. Carb one reads 2.5. Carb 2 reads 3. Carbs 3 and 4 read 11! I tried adjusting the idle/mixture screws and nothing happens. I have them all out now 4 turns. How can the vaccum reading be so different from carbs 1,2 and 3,4? Am I missing something obvious? There are four,houses coming off of the carbs, two from each. One goes to an inline fuel filter. One goes from one set of carbs to the other. The final hose goes nowhere and is capped off.
Any info that may help me will be greatly appreciated. Otherwise I will look into a carb rebuild. Thank you in advance

[AndyVAS]

Before you spend too much time on them, ask yourself how much your time is worth. I spent most of a week tuning, adjusting, and rebuilding a pair on an Alfa Romeo. When it was done they were close but not perfect. I will never commit to tuning another motor with those Dellorto carbs.

[sptcoupe]

From what you have measured, the carbs are not even close to being balanced and synch'd. I'm surprised it runs at all.

Do that basic tuning first and then you can get an idea of what to on jetting. Do you know what jets are in it?

[Pt6295]

The jets on top of the carbs are 60's and 120's.

[bobplyler]

I had an Italian Harley-Davidson 125 with a Dellorto carb. Once it got hot, it
wouldn't start without a 30 minute cool-off period.

[Pt6295]

a lot of people claim that the Dellorto and Weber are almost identical yet it seems the Dellorto are a lot harder to tune properly. I like the idea of Italian carbs on my fiat but hopefully they aren't more problems than they are worth.

[Pt6295]

An update. So I did some more checking and cylinders 1 and 2 are not firing. Compression is good on both at around 110-115 and valve clearance was good as well. Cylinders 1 and 2 are the same cylinders that are fed by the carburetor reading 1-2 vaccum pressure. I am out of ideas right now and I am leaning towards having the Carbs rebuilt. Any other suggestions? Thanks in advance.

[bobplyler]

Sounds like a vacuum leak. There are multiple ways to find these. Check the internet.

I just found this:
http://www.popularmechanics.com/cars/ho ... cuum-leak/

[Pt6295]

Thank you very much. I am going to try and find the leak. I have also decided to convert the manifold and carb to a 32/36 dfev for easier tunability. On the car is the original fiat waffle intake with dual Dellorto carbs. If anyone is interested in them, let me know.