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Posted by: vin man Oct 17 2018, 09:45 PM

I gave up on my Weber's and got a set of Dellortos. Had them rebuilt professionally and have installed on the new motor (1.8 built out to 2056).

I can't get them running without covering the air intakes on the carbs. I believe I have a vacuum leak somewhere besides thecarbs or intake manifolds.

Wondering if I missed some type of vacuum port on the engine itself. Anyone have a suggestion on where else air could be getting into the engine?

Posted by: VaccaRabite Oct 18 2018, 09:19 AM

I'm going to assume you are using dual carbs? Not a single carb running through the throttle body and down the intake runners?

have you gone through the exercise of balancing the carbs?

Anyway, I don't know Dells, but I did have dual IDF webers on my car for a few years and they are somewhat similar. There should be no open ports on the outside of the carbs. If there are any nipples with openings the need to be closed off. A google search will tell you where the vacuum ports are on your Dells.

But I bet you have other issues at hand. How do you know that they are not leaking through the intake runners somewhere? Have you checked?

Are the carbs properly sized for your engine? What size vents and jets are you running? Its very possible you are just moving too much air and you have to choke it off for the car to function.

And remember that the idle circuit is different from the mains, and your car uses the idle circuit a LOT.

We need more information before we can help here. And pictures.

Zach

Posted by: vin man Oct 18 2018, 09:38 AM

Dual Dellortos - yes.
Checked the intake runners with carb cleaner while running.
I had Webers 44s and these are Dellorto 40s. I'm not certain of jet size. Would need to pull carb off again and pull it apart to inspect jet size.
The 3 vacuum ports on each carb are plugged.
How would I know vent size?

I'll add some photos
http://s304.photobucket.com/user/e065206/media/Our%20Cars/1972%20Porsche%20914/IMG_20181018_084025.jpg.html
http://s304.photobucket.com/user/e065206/media/Our%20Cars/1972%20Porsche%20914/IMG_20181018_084037.jpg.html
http://s304.photobucket.com/user/e065206/media/Our%20Cars/1972%20Porsche%20914/IMG_20181018_084048.jpg.html

Posted by: rhodyguy Oct 18 2018, 10:14 AM

When you say 'covering the air intakes' do you mean covering the venturis? Like all 4 at one time?

The Del manual from CB sucks. BIG time. Wasted money. Is there a better manual out there?

Posted by: vin man Oct 18 2018, 11:04 AM

Putting my hand over one of the venturi's makes a significant difference. The issue is that it works on either carb. That's why I think there is a leak someplace else. Is there any port in the block or head that maybe I didn't plug?

Posted by: marksteinhilber Oct 18 2018, 11:52 AM

Where are your air bleed or bypass screws that should be next to each mixture screw?

Posted by: VaccaRabite Oct 18 2018, 11:54 AM

The "40" refers to the barrel size on the carb. The venturis are removable from within the barrel of the carb and probably look something like this:



They will be stamped somewhere with a number. For a 2056 you probably want a vent sized at around 28. Too big and you are going to get results like what you are seeing, too small and the engine will run out of breath at higher RPM.

You can get at your jets without pulling the carb all apart. At least you can with Webers, and I think you can with Dels. Your idle jet SHOULD be the brass screw with the red o-rings. 2 per carb. Your mains are visible if you remove the aircleaner. Again, take this with a grain of salt, as I was a Weber guy. They are similar but not the same.

The jets also need to be sized to work in concert with the vents. Again, too much air and not enough fuel will make it hard to start. You could try increasing your idle jet size to fatten up the mix at idle and transition.

And there is also that carbs just need a bit more gas to get going. Have you tried pumping the pedal a few times before start to get some gas in there? Then playing with the throttle until the car starts? Carbs that start easily when cold with have a very high idle when warm - which is why lots of cars came with chokes. Our webers and dells don't have the chokes, we have to manage that ourselves until the engine gets warm.

Zach

Posted by: marksteinhilber Oct 18 2018, 11:57 AM

Here, this might help. http://www.redlineweber.com/html/Tech/idf_adjustment_controls.htm

Posted by: marksteinhilber Oct 18 2018, 12:29 PM

OOps, sorry, you got rid of the weber 44s for Dellorto 40. My read of this tuning guide shows Dels also may have air bypass valves that seem like they should be where you have vacuum ports plugged. You may need valves in there to plug the passage that is letting too much bypass air through.

Posted by: marksteinhilber Oct 18 2018, 12:29 PM

This guide: https://sites.google.com/site/stpsgarage/about-me/dellorto40drlacarburetorrebuild

Posted by: rhodyguy Oct 18 2018, 01:42 PM

That's great one! Thank you.

To the op. Check that filter that lives in the Banjo fitting.