Just got the car on the road. Getting it ready for Carlisle. I'm having a problem with the carb.
1970 Challenger, 440, Auto, Stock, new rebuild on the carb.
Carb idles great. However, it won't pick up off idle. In order to get it to drive (feathering pedal) I need to turn the mixture up so now it it overly rich.
What's in the circuit that might cause this?

Sounds like your accelerator pump or accel. pump circuit . . . do you get a good pump shot out when you look down the throat and move the throttle ??

I always go back to the book on carb rebuilds, at least with my stock machines. Adjustments according to the service manual . . . is the rod adjusted correctly to provide the right amount of movement of the accel pump ??

Just my two cents worth . . . hope that helps . . .

Mark

Also check your advance curve....when going back to the correct 4640SA AVS for my '69 I had a terrible off idle stumble.
Originally I had my vac advance locked out on my dizzy when I had my 750 Holley. Turns out I was told AVS's NEED vacuum advance due to their lean idle nature. had my dizzy recurved by Don over at FBO to incorporate back my vacuum advance & problem solved for the most part....still am futzing with choke mechanism but that's a different topic....

Make sure your air valve on the secondary's isn't opening. Then it most likely it is accelerator pump circuit. Look in there and make sure you are getting a good squirt. If not, find out why.

I won't be much help here but I had the exact same problem with two 440 avs carbs. I tried everything I could think of and I still don't get a good pump shot. I tried several pump plungers and adjusted the arms in every conceiveable way but still not better. I know I am missing something but I have never figured out what it is.

I read somewhere that the check ball assy,the one on the feed side into the bowl area can leak back.The shot instead of going to the squirters goes back to the bowl area.Maybe worth looking into. John.

If the carb is a recent rebulid, perhaps the accel pump plunger is folded back and not sealing.

I've rebuilt two AVS carbs for personal use, using Walker rebuild kits from Larry Isgro Carburetors. They work really well.

On both rebuilds, I found it took a lot of time and care to install the leather accel-pump plunger without the leather gasket edge folding back on itself in the accel pump bore.

Ron have you checked the pump spray yet,
we're waiting to see if you're going to
make the trip O.K.

I checked the pump spray while not running the engine and it seemed fine. With the engine running, it still hesitates/bogs/gasps.
I measured the accelerator pump height and tweaked it a bit (raised it about 1/16), but that didn't seem to help much.
I put the air cleaner on and things improved. Is the restriction of the air cleaner, and the connection of the vacuum line on the back of the carb an indication of anything?
I set the timing with the air cleaner off, so maybe I need to adjust it with the air cleaner on.
Thanks for all the input.

Is the check valve under the spray nozzle
in place? Sure sounds like accelerator
circuit not spraying - Enough.

I fought this last summer and concluded that the bore for the pump was a little out of round or wide in some spot.

It gets better when the car warms up and it swells just a bit. Still get a dry shot every now and then when warm.

I had the top off and worked the plunger by hand at one point. Just no shot for no real reason sometimes. Tried cleaning by soaking, starting fluid, you name it.

I just live with it now. Great carb other than that.

I would replace the check valve that lets fuel into the well, if it is not holding it will let part of the shot return into the fuel bowl. Also replace the pump with one from edelbrock. They are made of vi-ton or a similar material and work well.