Carter AVS Lean Spot

[kawahonda]

Choke is on (I still have to do it by hand, the bi metallic coil doesn't give it enough upwards pressure to open the choke)....unless something else isn't right.

Set screw isn't near the steps on the cam...

[kawahonda]

Solved the divorced choke rod issue. Basically, it wasn't applying enough upward pressure to "overcome" the slight friction in order to flip the choke plate closed. This is likely because of the 5/16" (or whatever) carb gasket I am using for heat soak. A couple minutes with pliers allowed me to lengthen the rod in order for it to accurately 100% apply the right amount of pressure when cold.

Yay, no more having to pop open the hood to "flick" up the mechanism anymore.

Now, to figure out how this fast idle/cam linkage thing works.

[734406PK]

Check the factory shop manual (FSM) for the best procedure explanation on AVS linkage adjustment. Fairly simple bending of link rods to a  specific dimension. Congrats on solving your issue!

[kawahonda]

I ordered a step up spring kit for final tuning.

My understanding is to warm engine, place in gear, and read vacuum.

Divide by 2, and go with that spring?

I have not tested my vacuum in gear, but I'm 16" in park. Probably 14-15 in gear as a guess.

I assume the factory Carter ones are 8?

[734406PK]

I ordered a step up spring kit for final tuning.

My understanding is to warm engine, place in gear, and read vacuum.

Divide by 2, and go with that spring?

I have not tested my vacuum in gear, but I'm 16" in park. Probably 14-15 in gear as a guess.

I assume the factory Carter ones are 8?

Yes that's the Edelbrock recommended starting point for metering rod springs 1/2 idle vacuum in gear. Keep in mind that the lower the spring tension the later the metering rods come into play (lift off from cruise to power). OEM are probably 8-10 inHg springs when new. They are color coded today.   

[kawahonda]

Cool. Sounds like firmer is better and I should prob leave it alone at my vacuum. At least I have them on hand!

I'll continue to look at the fast idle engage. I have a rebuilt AVS on the desk and it also does not engage the fast idle during bench testing.

Would be nice if someone could shoot some pictures of a know working one so I can see how all the linkages should work.

[Bullitt-]

Cool. Sounds like firmer is better and I should prob leave it alone at my vacuum. At least I have them on hand!

I'll continue to look at the fast idle engage. I have a rebuilt AVS on the desk and it also does not engage the fast idle during bench testing.

Would be nice if someone could shoot some pictures of a know working one so I can see how all the linkages should work.

This should do it   http://www.moparts.org/Tech/Archive/fuel/14.html

[kawahonda]

Here's the problem with mine, and the one on my bench. Maybe I still don't understand how it works.

1) The bimetallic choke will apply upward pressure when engine is cold This will push the choke plate closed using the linkage on the passenger side of the vehicle. Solved by lengthening the rod to account for carb spacer.

2) This same linkage runs through the carb and "kicks" this flipper on the driver's side of the car. I marked the flipper. There is only ONE way to install this, because the flipper has a pre-drilled location for this linkage that runs through (aka, non-adjustable).

3) That flipper then "kicks" the surrounding linkage.....SUPPOSEDLY enough to kick the cam under the fast idle screw. This just ain't happening, or it's not anywhere close to opening. This surroudning linkage doesn't move at all, choke on or off.

[73_Cuda_4_Me]

Make sure the tab on the upper arm contacts the plate (flipper) and pushes it counter-clockwise, pulling the fast idle rod upwards...

If that is making good contact, and pulls rod upwards, then check to lower pivot plate to make sure that it isn't seized on the shaft...

You should be able to move everything by hand freely, and get fast idle screw to hit cam...

[kawahonda]

Yep, the tab contacts plate on the driver's side, but the allowable movement isn't enough to really rotate enough to cause a big movement of the fast idle cam area.

All pivots move freely. Nothing appears or seems seized.

To make sure I understand operation correctly.

It all starts with the choke, either from the choke well or from an electric choke. When cold, the linkage (from the choke unit) on the passenger side develops pressure and applies it to the passenger side choke linkage that will "push" the choke on (the choke plate closes). This linkage connects to the driver's side (via inside the carb) and pushes the flipper on another plate, which pulls the bottom linkage towards engaging the fast idle cam. HOWEVER, without any movement of gas pedal, I would EXPECT that the edge of the fast idle cam (not the "engaged face") will push against the fast idle cam screw (under some pressure). Once the throttle is activated (probably around 1/2 way is all that's needed for a few pumps), the fast idle screw gets "out of the way" and allows the cam to lock into the fast idle position. From here, you simply just fire up the car. As the engine warms up, the choke plate will slowly open, which in turn will rotate the fast idle cam to a lower RPM "notch" during warming. As soon as you "blip" the throttle with the choke is fully off, the cam should rotate out of the way.

Do I at least have the mental model down on correct operation?

If so, the cam is not pressing against the edge fast idle screw when the choke is activated.

What I really need to see is a series of actual pictures of an AVS with a working fast-idle linkage from start to finish, where/how all linkages are positioned, and maximum movement of each. Seeing pictures of AFBs, Edelbrock AVSs, etc doesn't really help since the minor differences/different linkage designs won't be fully applicable.

My dad is coming into town tomorrow and is excited to solve this. But I'd always strive to solve it before him, or at least, go into it with the correct mental model of operation with him.

What's interesting is BOTH of my AVS carbs perform this way, and are assumed to be assembled correctly. Not having fast idle cam operation is not a deal breaker or anything, but it's nice to have.

Maybe I can shoot a video of the AVS on the bench and post it here.

[Chryco Psycho]

You are correct in your understanding of the way the carb should be working 

[bennydodge]

Nice to see you're getting a handle on the tune-amazing what a little extra fuel will do  . Make sure that you depress the throttle FULLY on a cold engine(sitting overnight). This will completely engage the fast idle cam. 

[Bullitt-]

better PDF https://quadrajetparts.com/pdfs/4052C.pdf
Figure 5 is the adjustment I think your needing ...



Here's a similar unit for reference ... DO I see one major difference in the upper shaft items in the way they are assembled ?


another put together the same way
http://www.2040-parts.com/-68-69-chrysler-dodge-plymouth-carburetor-4711sa-c-4-avs-340-383-413-4-bbl-i529815/

[kawahonda]

Oh hell!

That explains it.

[734406PK]

better PDF https://quadrajetparts.com/pdfs/4052C.pdf
Figure 5 is the adjustment I think your needing ...



Here's a similar unit for reference ... DO I see one major difference in the upper shaft items in the way they are assembled ?


another put together the same way
http://www.2040-parts.com/-68-69-chrysler-dodge-plymouth-carburetor-4711sa-c-4-avs-340-383-413-4-bbl-i529815/

YUP, Good eye!