Carter #4401 AVS carb

[GTO Geoff]

This carb is off a 383 Dodge. I noticed something on it that I have not noticed on other AFB/AVS carbs.
With 0.040" of t/slot showing, the vac adv port is exposed. Since most factory carbs are set up with ~0.040" of slot visible at idle, this carb would have vac adv at idle. Other AVS carbs I have show 0.060" of t slot exposed & the vac adv port is still covered by the t/blade. I am wondering if the 4401 has a manufacturing fault.

[rgalajda]

I have 4615s and a 4611sa AVS carbs here and they are both about the same as you are saying. At .035" t-slot the port is just starting to be exposed.

I am just starting to do a restoration on the 4611sa , 1969 340 carb. Thinking about converting it to regular meeting rods instead of 3 step rods.
1) replace domed rod cover plate with standard flat cover
2) replace piston ( original piston was 2 stage )
3) replace tall main jet with standard jet
4) use standard AFB/edelbrock rods

I believe you can also use the carter 9000 series / edelbrock accelerator pump

[GTO Geoff]

Thanks for the reply. The 4401 carb has the smaller 3/4" acc pump plunger. I believe at some point in the AVS range this was enlarged to 13/16", which is what Edel uses. Not sure which carb # was the changeover model.
Your carb [ shown ] & the 4401 would have been pulling vac adv at idle with the 'normal' 0.040" of t/slot showing.
Since everybody tells me Chry only used PVA, I wonder is this a manufacturing fault that somehow escaped detection.

[rgalajda]

Since all three of these carbs have idle bypass air ( at least mine do ) , I'm thinking these carbs idled in the closed throttle position similar to some of the rochester 4 G carbs did. No exposure then.

[GTO Geoff]

Idle bypass air. Are you talking about the single LH thread screw, near the top of the carb body?

[GTO Geoff]

Rg,
Thinking more about this. I do not think these carbs were designed to idle 'closed throttle'. My GTO had an AFB on it & did idle with closed t/blades, but there were important differences:
- it had a large brass screw in between the mixture screws that controlled idle speed with more/less air. The air passage it controlled was quite large so that there was a wide range of idle speed control
- it did not have a conventional idle speed screw. The boss was there on the side of the carb, but undrilled.
- the pri blades were thick[er], I guess to prevent jamming.

Back to the AVS. The idle mixture screw holes in the t/bores were tiny, about 1/16". They are part of the air source for idling. The LH air screw on all carbs I have seen never passed enough air to control idle speed per se, just enough to 'trim' the mixture. If the blades are closed, a substantial amount of air is blocked from entering the engine [ plus, from the t/slot ]. So where would this carb get it's idle air?

[rgalajda]

Does your AVS 4401 have idle bypass air like in this picture of mine?

[rgalajda]

Your carb looks like this

[GTO Geoff]

Yep, plugs covering the mixture screws. I removed the plugs, warmed the body with a heat gun & dribbled ATF into the holes. Screws were tight, but was able to turn them once cooled down. Probably some sort of sealer on the screws to stop vibrating loose. I didn't remove them.
Idle air screw also, as pictured.

[rgalajda]

ADJUSTABLE OFF-IDLE
AIR BLEED
Some older AVS models use an "adjustable off-idle air
bleed" which is adjusted during flow test. This adjustment
should never be changed as it cannot be adjusted
in the field.
The purpose of the "adjustable off-idle air bleed" is
greater control of the air-fuel ratio at flow rates above
curb idle, resulting in substantial reduction in hydrocarbon
emissions.
The air bleed valve is set to open at an idle port vacuum
of 7 to 12 inches of water, which is slightly above the
three to four inches at curb idle. When the throttle is
opened slightly, the lower pressure at the idle port
opens the air bleed valve to control the air-fuel ratio.
When the throttle valves are opened a certain amount,
the vacuum ~t the idle port will drop below the 7 to 12
inches of water, allowing the air bleed valve to seat.
This enrichment of the air-fuel mixture is desirable for
a high rate of acceleration.
The air bleed valve will open on deceleration from high
speed to prevent rich mixtures.

I found on my avs 4611 this screw was adjusted about 1/2 turn open from seated.
On the AVS 4615 which has an idle air adjusting screw , the screw in the below picture seemed to be fully seated (closed)