(2) carter avs's stumbles badly from a stop-anyone else have this issue??

[minnesota guy]

I took my 1969 440 GTX to the drags over the weekend at BIR in Brainerd, MN. It is set up in stock trim. 452 heads, AVS, Auto, 4:10-in 8 3/4; Stock "Bullet" camshaft. It ran a 13.62 @ 102 in very humid temps.

Unless super heated, the Carter AVS would stumble and quit at the starting line. I have played with the secondary door. Doesnt seem to help. Set jetting on the richer side at .106 each, squared.
Original carb was the 1969 4640. (750cfm)

I tried my 1971 AVS 4968 (also 750cfm) This one I used on my 71 Cuda, and it never stumbled at the drags. I am a little befuddled. I get a good solid squirt.

I have an HP Carter mechanical up front. The 69 came with a fuel separator instead of a filter which I don't use. I have always noticed a stumble since the rebuild--trying about 3 different Carter Avs's...
Do these cars have issues with the gas tanks breathing properly? It is original tank.

Could I have a vacuum leak somewhere? Intake is plugged in the back. It idles--finally-after warmup....

I installed an electric carter fuel pump in the rear as well...to no avail on the stumbling issue.

Once it gets past that stumble point, it really takes off.
Embarrassing to cut an .000 light --which I finally did!! but then it quit. I can always toss on a 750 or 850 DP Holley...
Just seems to be the Carter AVS??

What do you guys think? Interested in comments.

Thanks. Jeff

 

[67 coronet]

since its better when warm,how are the choke settings?odd that it does it with several diff carbs,problem would seem to be some place else.easy to check for vac leak.start to cover carb with your hand while idling.smoothing out or rpm rise indicates vac leak.starting to stall means it is fine there.

 

[minnesota guy]

Thanks. No choke plate. Good idea. I will do that. I checked my HP mech pump last night, disconnected and it gave a huge shot of gas to the driver fender. I can rule that out it appears. I have Blocked the factory cross over as well, as that costs HP at the drags, but once car is warmed up that shouldnt matter. I am going to test my 750 DP on it.

 

[lewtot184]

i have a 4618 on my '69 r/t and it runs great. i did a few mods to it though. i use the edelbrock viton accelerator pump. the original leather pumps were never reliable. i use a small carter squirter, .031", but an edelbrock .028", with minor mods, would work great. i have the mixture screws at the bottom of the carb replaced with edelbrocks. i opened the idle jet to .040" and use .101" primary jets with 16-575 rods. secondary jets are .098". this combo is great for my engine.

 

[MCODECUDA]

I run a stock intake with the crossover blocked and a stock AVS. I have the choke flapper and rod removed. If I race it I have to make sure that the intake and carb is warm or it will bog on me also.

 

[Hemirunner]

Sounds like it's going dead rich at launch. Did you play with accelerator pump settings? Did you check the floats? Are you running the off road needle and seat assemblies? Fuel pressure above 6psi plays havoc with the needle/seats.

 

[minnesota guy]

Idle Jet..You talking where the idle screws -screw into?