Rough idle Carter AVS

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Here`s the holes for the screws which are now open for adjustment.

IM000745.jpg


IM000735.jpg
 
HOLY FREAKIN MOLY!!!!!!!!!
Now that gets an award to the do-er of that mod. I'm not sure if dumbass is quite right, but we'll work on it !!!!
 
i'm glad you got it figured out. is that the idle air bleed screw you have on top in the middle instead of a curb idle screw on the side?
 
Longgone said:
I have not had the carb apart. It was just rebuilt by a reputable dealer and is supposedly ready to plug-in and play. Could the intake be leaking on the inside?
Click to expand...
That just sux ! You should tell the world who NOT to take their work to.
 
I just want to thank Longgone for this thread and Forabodiesonly for their superb site. I also have a 1968 GTS with the stock 340 and Carter AVS 4425S carburetor. It's an orginal California car which may have had an effect as well.
I could not get a smooth idle either and i went through everything. After reading this thread, I pulled the carb off and sure enough, my screws were also screwed all the way in and leaded over. The leaded over is correct for this carb.
After removing the lead and backing out the screws, then adjusting the air bleed screw, my idle smooth out big time!
My mechanic was looking at intake gasket, cam, new carb, etc. before this.
Thanks again to Longgone and this site!
Bill
 
Hello Bill, I`m glad this thread helped you out. I get a lot of info from this site . FABO rocks! :headbang: Oh , and to clarify one thing, the picture in post 26 is NOT of the rebuilt carburetor.:-D
 
How do you remove the lead that covers the idle mixture screws?

Drill?, heat?, Awl?

What has worked for you? I am having similiar poor idle problems and would like to see if adjusting the screws works.
 
69swinger340391 said:
How do you remove the lead that covers the idle mixture screws?

Drill?, heat?, Awl?

What has worked for you? I am having similiar poor idle problems and would like to see if adjusting the screws works.
Click to expand...

Drill it out. A left hand bit would be the optimal thing if you can find one, that way when you punch through the lead and hit the screw head it doesn`t grab and twist it in any further.
 
Dan Squires said:
In 1968 Chrysler starts to use the Carter AVS carburetor. They incorporated a number of emission features within the carburetors. These are the features they incorporated;
  • Sealed off the idle fuel mixture adjustment screws which means that you can't adjust the idle fuel mixture. By the way, if these needles aren't removed during cleaning then dirt and debris get caught in the circuit further reducing the idle fuel to the engine. And when this happens the carburetor runs leaner. Most people do not remove these when cleaning the carburetor because they are sealed off.
  • Added an air bleed adjustment screw (most carburetors use 2 idle air bleed circuits, this screw added a third one), which means you can add more air to an already lean mixture.
  • Used smaller idle fuel pickup orifices in the primary venturi clusters, which means you can only pull in so much fuel for idle. With todays gasoline you need more fuel at idle because of the alcohol-type additives in the gasoline.
  • Incorporated a fixed idle air bypass circuit. This can be beneficial sometimes, but for the most part this circuit should be shut-off. My policy has always been deactivate this circuit first then reactivate it if needed. GM Quadrajets have this circuit also and I know this from my experience with Quadrajet carburetors.
  • Added a clever device that introduces additional air when the throttle plates go off idle. However if you have to open the throttle plates more than normal to get the car to idle then you activate this device. And when this happens more air is added to the idle mixture. Also, as the carburetor gets older the spring looses its tension against the check ball that shuts off this device. When this happens the check ball opens up the passage and allows additional air into the idle circuit. More air means more leanness.
Fortunately all of this can be corrected. However the corrections require the following;
  • Thorough knowledge of the AVS idle and off idle circuity
  • Special tools
  • Special parts
The write-up to correct this is lengthy. I can prepare this or I can discuss this with anyone who is interested. I can also make the modifications for you. I modified a 1968 AVS 4426S (383 manual transmission, I believe the 1968 383 Road Runner used this carburetor) and tested it on a carburetor flow-bench which worked fine.

I'm not trying to sell anybody anything. I've been doing carburetor restoration and repair for the past 15+ years. Most of my work has been with GM products. However I have a fondness for Chryslers (Dodge and Plymouth too).

If you have a question then please feel free to contact me. My name is Dan Squires and I can be contacted at
(630) 551-0595
[email protected]
Dan's Carburetor Service

Thank you very much for reading this.
Click to expand...

Great info Dan, thanks!
 
Longgone said:
It`s the original carb, just rebuilt.......didn`t run all that great before rebuilding but this is a new rebuilt engine now with new rings, bearings, cam, ignition, etc.. The more I read about the carb and tuning ,the more it points to a vacuum leak somewhere. I`m almost ready to change the manifold and carb gaskets out just to rule that out. The car has 13-15 lbs. of vacuum at 850 rpm and I`ve used carb cleaner and checked all the gaps for leaks with no increase in rpm.???
Click to expand...

68 only AVS carbs have a single screw idle adjustment above two plugged mixture screws. I believe early AFB hemi's have the same setup.

The screw is just a controled vacuum leak and causes those carbs to not have the idle qualities as the 69-71 AVS's without that screw and 2 unplugged idle mixture adjustment screws. Not real bad, but RPM will very some at idle.

You may (probably) have a problem bigger than that. But the is an inherent issue that make it real tough to get a picture perfect constant idle.
 
billkrz said:
I just want to thank Longgone for this thread and Forabodiesonly for their superb site. I also have a 1968 GTS with the stock 340 and Carter AVS 4425S carburetor. It's an orginal California car which may have had an effect as well.
I could not get a smooth idle either and i went through everything. After reading this thread, I pulled the carb off and sure enough, my screws were also screwed all the way in and leaded over. The leaded over is correct for this carb.
After removing the lead and backing out the screws, then adjusting the air bleed screw, my idle smooth out big time!
My mechanic was looking at intake gasket, cam, new carb, etc. before this.
Thanks again to Longgone and this site!
Bill
Click to expand...

I've tried to get the lead out of my 4425 but I still can't turn the screws. One is way more turned in than the other :sad6: I don't want to break off the flat in the idle screw.

I've been running a holley 1850 and a 71 AVS on both my 68's.
 
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