One question: in my personal experience, I've noticed that pre EGR and post EGR Holleys 1920 carburetors have a different grooves in the base. When installing a EGR carb in a non EGR intake, there is high vacuum in the power valve and choke puller system, which tells me the vacuum source is somehow related with the EGR valve plumbing at the intake. I modified an EGR carburetor to install it in a non EGR intake (minor modifications) and I'm happy with the results, but:

-Can you install a non EGR carb in a EGR intake?
-Is there a carb-intake gasket that allows to use a EGR carb in a non EGR intake with no mods?
-Does the EGR valve fails closed? If no vacuum is connected to the EGR valve, is it going to remain closed?
-When you remove the EGR and put a blind, you lose the seal in this vacuum source, so: do you need to modify the carb or use a non EGR carb for it to work properly.

Some of this questions might explain some reports of abyssal fuel economy from few owners that might not have checked how hacked is their engine, or did the best they could with what they had, o simply stuck parts together until the engine revved...

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/6 Dodge Charger 69
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Yes, in most cases you can use the early date correct gasket on the late intake... (i.e a 1967 carb and gasket on the 1976 intake)...
It depends on how the carb is configured, and how the intake is configured....If the vacuum ports or power valve ports use a divorced hole in the carb mounting surface then there will be problems, if the ports draw from the throttle bores under the throttle plates then it would have a better chance of success....for our 1 barrels you can compare the gaskets used by the 1920's vs, the 1945 to see what differences are there (other than gasket thickness...
That's fairly subjective...If the EGR valve does not seat correctly, and the engine is not in best shape the EGR valve could be off it's seat and carbon builds up could plug it up, or some carbon could build up under the valve lip keeping it from fully seating if still being used. Typically if there is no vacuum to the EGR valve actuator it should not open... although I would be curious to see if the valve can be bumped off it's seat of a backfire occurs.. Either way, because there is a chance there could be a problem, it's best to flip the EGR or remove and plate it if you are not required to have this equipment per local regulations.
When you flip the EGR so the ports don't line up, or put a plate in it's place, you always need to use sealant or a gasket as the ports in the intake are still open to the exhaust manifold on one side, and the intake plenum on the other....Some people have threaded and put a plug where the passage to the intake is. Ultimately if you don't seal anything, it's a vacuum leak that needs to be corrected. You should not have to modify the carb other than capping the EGR nipple at the base plate....

If you really think about how it works, all that the carb port serves as a vacuum source for the system...in the most basic version: the hose goes from the carb to the vacuum temp switch at the radiator (since the EGR is only to function once the engine is at operating temperature), then the hose runs to the EGR....once you cap the port, (and use a quality cap), everything else downstream no longer functions, and there should not be a vacuum leak..


The best way to understand how the carb and it's vacuum system works is to pull a core apart, and see what passages serve what port, and where they draw their vacuum signal from. You may find that some passages are interlinked and may cause problems with interrelated circuits in the carb, or some may just be a hole to the bore under the throttle plate for constant vacuum...

One last food for thought though...in some cases over the years, specific carbs may have been specifically calibrated for a certain model (jetting, linkage settings, idle circuit, transition slot position and length).... most carbs have a "wide" range to them so they could be used on several models of vehicle and you can install them on most vehicles of a similar weight and options...

Looking at holley egr carb no 6594. Vacuum groove is different, Vacuum is obtained threw a notch in side wall of carb at base under throttle plate Also has hole in throttle plate. Holley no 3279 non egr carb, no notch vacuum comes from hole or notch in base gasket. Using this carb with the wrong gasket would block vacuum to power valve and choke puller, no hole in throttle plate. In the past ,some memory of cutting notch in gasket to match carb.The pcv valve port is also different.The egr carb port for pcv is threw side wall of carb under throttle plate. The non egr carb port threw base gasket and either a notch in gasket or hole in gasket to matching hole in intake. I do not remember for sure.

http://www.carburetor-parts.com/Carter- ... _1442.html Notches and holes

http://www.carburetor-parts.com/Holley- ... _1448.html Just holes ,Click on picture to make bigger. Heres a guess,the older manifolds had a small hole for pcv under carb flange, that lined up with hole in gasket. Wrong gasket blocks this hole. The gasket in link can be notched at correct hole to let vacuum to pcv. The older carb can then be used on later manifold.

Heres the hole, for early pcv,later manifold no hole http://www.slantsix.org/articles/Efi-Ma ... nifold.jpg

Presence/absence of EGR passages and valve mount is the only difference between intakes with vs. without EGR. The carb mount flange is the same (though late-production 1bbl intakes do not have the 1/4" hole adjacent to the outboard carb mount stud). All you have to do is use the correct carb-to-intake gasket for the carburetor being used.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thank you all. So there are no differences in the intake, except the PCV hole. Here are some pictures of the carb bases:

For a 1969:

https://flic.kr/p/tcYG6Z

In the base you can see hole for the economizer al 11:00 o'clock and the hole for the diaphragm valve at 2:00 o'clock. They share the same vacuum source.
The carb number is

https://flic.kr/p/tcYFHV

In the 1973

https://flic.kr/p/taBaZf

You can see the same holes, but the groove extends to 4 o'clock, and it has a notch, connecting it to the vacuum at the carb base. This picture is clearer

https://flic.kr/p/sVkBuS

The carb number is:

https://flic.kr/p/tcYEUF

If you install the 1973 carb in the 1969 intake, there is always vacuum in the choke diaphragm, and in the economizer (vacuum source at carb base, well below butterfly). I modified it sealing the groove with a drop of epoxy at the bushing level (3 o'clock), filled it level with the carb base, installed the carb, and then installed a tee in the diaphragm tube and connected it to the canister intake, so there will be vacuum in the system only when accelerating (vacuum source just above the closed butterfly). My car has no charcoal canister, so that port was capped anyway.

I was thinking the EGR somehow controlled the opening of that notch at 4 o'clock via a modified intake flange, but I guess it was something else, my mistake for the misleading thread title.

Other option is that it had to do with emissions, but is kinda weird having the thermostatic sensor and the diaphragm fighting each other during startup, and having the diaphragm always with vacuum (that can reduce the diaphragm live...)

If somebody knows better how the diaphragm - Economizer vacuum was controlled in the 1973 carb with the opening I showed on the carb base, please let me know.

Thank you!

PD: edited May 19th 2015-Changed link to pics

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/6 Dodge Charger 69
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This is bad idea. I have carb on desk in front of me,understand theory, Just not going to work right. Choke pull-off diaphragm,economizer,Air cleaner temp sensor all need full time manifold vacuum.

…except the ¼" hole adjacent to the outboard carb mount stud. It was the PCV hole for '63-'67 Carter BBS and Holley 1920 carbs (plus '61-'62 cars equipped with PCV). It was the power valve vacuum feed for the '63 Stromberg WA. It was the thermostatic air cleaner vacuum feed for '70-'72 BBS and 1920, and was used to send manifold vacuum to various other places on various carbs in various years.
…with the correct 1973 carb-to-intake gasket, the carb works as it's supposed to, because it has no way of knowing what year manifold it's on. There is no reason or need or benefit to glooping up the carb with epoxy or other stickum, nor to otherwise hack the carburetor or the manifold. Just use the base gasket appropriate to the carburetor, and you'll be fine without causing new problems.
Which diaphragm line are you talking about? There is the air cleaner diaphragm and the choke pull-off diaphragm. Also, why did you do this hack? If your car has no charcoal canister (because it is a pre-'72 model), but the carb is configured for a car with a canister, just plug the charcoal canister port on the carburetor. Connecting the carb's charcoal cannister port to the air cleaner or choke pull-off diaphragm line means you've effectively created a vacuum leak and spoiled the function of the thermostatic air cleaner or choke pull-off.

The choke pull-off and the air cleaner diaphragm (via its thermostat) are supposed to get manifold vacuum without regard to throttle plate position, by the way, and so is the "Economizer" diaphragm. Not just during acceleration!

If your car does have a charcoal canister (and it should! What provision did the nitwit previous owner make for safe and effective fuel tank and carb bowl venting?), it needs to get hooked up this way.
The EGR system works as described in the factory service manual. Briefly: the venturi vacuum signal is ported via a hose to the "vacuum amplifier" (hockey puck shaped device mounted about midway back atop the cylinder head). This is a vacuum relay; when the venturi vacuum signal reaches a certain threshold, the "amplifier" sends manifold vacuum to the EGR valve to open it—that is if the cooolant has reached operating temperature.
Other option to what, is that what had to do with emissions?
I can't imagine what you are seeing, but there is no such fight.
Eh?
The "Economizer" diaphragm sees manifold vacuum via internal carburetor porting, not via any vacuum hose.

It sounds to me as if you have artfully replaced the previous owner's random underhood hack-'n'-slash with a different but equally random underhood hack-'n'-slash of your own, rather than reading the appropriate manuals, learning how the various systems work and how they're supposed to be hooked up, and fixing them. Your epoxy maneuver and tee into a line that didn't need teeing were the wrong things to do, will cause problems rather than solving them, and demonstrate that you urgently need to bolster your knowledge. Guessing and assuming won't get you where you want to go.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

matv91, Dan: thanks for the warnings. This is a public board, is good that all that is posted here is sound. I'll check your posts and manuals, and will post later with a proper response. Thanks.

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/6 Dodge Charger 69
...there's nothing like using the "Search" link above to solve most of your problems...

The picuture links do not work,for me anyway

If somebody knows better how the diaphragm - Economizer vacuum was controlled in the 1973 carb with the opening I showed on the carb base, please let me know.

I can not see your pictures. Is there a brass piece with small opening pressed into port that feeds vacuum to economizer? Also does the throttle shaft at fuel bowl end of shaft,when turned wide open have holes that line up with holes in flange?

Already asked and answered. The "Economizer" diaphragm sees manifold vacuum via internal carburetor porting.
Some carburetors have a hole in the throttle plate. This has nothing to do with holes in the carb flange, it's for idle air calibration.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Matv91,

Sorry, I've had no time to sit and prepare a proper answer. I changed the picture links, let me know if you can see the pictures now.

_________________
/6 Dodge Charger 69
...there's nothing like using the "Search" link above to solve most of your problems...