I have a '69 AVS, 4618S, and am wondering about a few things. This plug is supposed to cover an off idle adjustment screw, according to the FSM. Should I gain access to it for cleaning and adjustment?



There is a spring inside that presses against a ball bearing, and on the top, it opens to the atmosphere.



It allows extra air to enter after the idle mixture screw, which itself just adjusts how much the idle fuel is diluted.



This is where the air comes from that goes through the idle mixture screw, and into the idle circuit.



This is where the idle limiter screws, as the FSM calls them, are located. They are covered by a plug and staked in. Should I gain access to them for the rebuild also?



Finally, there is this thermostatic air bleed, which I thought was only on A/C equipped cars, like the 4640S carb. It looks like it opens to a blind hole. I don't see any holes inside. Wonder why they wouldn't eliminate it on carbs that aren't drilled for it.





Why are the Edelbrock mixture screws up on the diagonal part, and the Carter has the same plugs next to the PCV port, and their mixture screws are below those?

My AVS carbs are the slightly later 2 screw design but the info below may be of some help.

http://www.forabodiesonly.com/mopar/showthread.php?t=50847

http://www.forabodiesonly.com/mopar/showthread.php?t=29582

and here's a link to how I converted my Carter AVS to annular boosters

http://www.mymopar.com/forums/index.php?showtopic=9065

On your bottom photo where the tip pf your pencil is pointing , those WERE the idle mixture screws , they are broken off because the steel screw is frozen in the cast alum body .

maybe, but not necessarily. Can't quite see. Those were emissions carbs, and on a virgin carb, there was a lead plug over the mixture screws. The screw head was recessed deep into the carb below the plug. An early attempt to prevent owner tampering.

Two of the biggest problems I have found with Carter AVS carbs is vacuum leaks & poor parts availability.

Look for wear on stepup pistons, rods, the primary jets are most likely oversize/oval, the throttle shafts especially the primary is most likely worn & mayme the body of the carb. The hot air compensator valve needs checked as the bimetal strips fail, is this the valve that you think goes to a blind hole? it usually is open to the botton of the carb.

Only buy good quality rebuild/gasket kits, I have had trouble with sub standard gasket material failing with modern gas & the thick insulating base gaskets in some of the cheap repo kits are not worth a pinch of sh!t.

If you find a source for spare parts (other than rebuild/gasket kits) at a reasonable price please let me know.

Actually,the casting has provisions for mixture screws in both locations depending on year and application.If not used they are plugged.Here is a 70 4spd I recently finished.Note location.I have taken a lot of carbs with the one screw,which incidently is a left hand thread and eliminated it and went with two screws in the base.Much easier to tune.Also,on the carbs with one mixture screw,you will find pre-adjusted mixture screws behind the plugs in the base due to emission requirements.

Here's one of the early style

This is an interesting thread.

Thank you.

I love my Carters!

interesting indeed

I fixed the pics I messed up on showing the thermostatic valve.

This is very interesting I have 3 69 383 4bbl carbs and they all have mixture screws where those supposed plugs are ?

I did have a 68 carb that had to one up top, but I can't remember if it also had the screws at the bottom also ?

John your 69's are typical, the early 68 AVS carbs had the single adjuster, most later 68's had two adjusters as your 69's do. I have also seen some 69's with the single adjuster, not really sure why they came both ways.

I think the 4618S had the single air bleed screw up top, and the 4618SA eliminated it, and added conventional adjusting screws where the idle limiter screws were in the earlier series. Perhaps it didn't accomplish it's goal, like the carbs were too lean, and getting lean misfires at idle, thus defeating the purpose of the leaner, reduced adjustability design.

The "SA" carbs were replacement carbs and would have had the later style adjusters.

Ever see one with all 3?

Hey 375inStroke can you post a photo of the base of your carb please, I'd like to see the underside.

I can't find any single screw carb bodies & this 2 screw one is dirty but you will get the drift. The port the pencil is in goes all the way through from the hot idle compensator valve to the base of the carb on all the carbs I have, some of them have a vacuum port low on the carb that comes off this port for the flaps in the airfilter snorkels.

I'll post a pic later. There is a passage in the bottom like your carb, but it doesn't go all the way through. On top, where the valve is, the port goes down about 3/8", and stops. There isn't a plug or anything. It is the casting itself.

Cheers, like I say all mine have the port all the way through & they are all different models, some 625cfm 383 some 625cfm 440 & some 750cfm 440 carbs but all of mine have 2 idle mixture screws. I will check through some other info I have & post again later tonight (NZ time)

The FSM says the thermostatic valve is for A/C equipped cars. Are any of those carbs for non-A/C equipped engines?

My 68 SM says the top screw is a off idle adjustment and the two screws under the plugs are factory set, maybe its a 4-speed thing. BTW the carb in the pic is a 69 but notice the dashpot for the 4-speed cars.

"I have a '69 AVS, 4618S, and am wondering about a few things. This plug is supposed to cover an off idle adjustment screw, according to the FSM. Should I gain access to it for cleaning and adjustment?"

What is the build date of your carb/car?
I suspect it is quite an early '69 440 Auto, non air car.

I wouldn't remove the plug.

"This is where the idle limiter screws, as the FSM calls them, are located. They are covered by a plug and staked in. Should I gain access to them for the rebuild also?

Not unless you have to, test run the carb first & if it can be adjusted OK with the one screw, leave the plugs well alone.

"Finally, there is this thermostatic air bleed, which I thought was only on A/C equipped cars, like the 4640S carb. It looks like it opens to a blind hole. I don't see any holes inside. Wonder why they wouldn't eliminate it on carbs that aren't drilled for it."

I have no idea as all my carbs are drilled but be thankfull it is not drilled as it is a common place for a vacuum leak that is very hard to find, the bimetal strip can fail or the valve not seating properly can have you chasing your tail or adjusting something else to compensate.

"I think the 4618S had the single air bleed screw up top, and the 4618SA eliminated it, and added conventional adjusting screws where the idle limiter screws were in the earlier series."

Right on the money

Later carbs with "SA" part number suffix have revised idle system (2 idle mixtute screws with limiter caps)

"The FSM says the thermostatic valve is for A/C equipped cars. Are any of those carbs for non-A/C equipped engines?"

Yes 3 are non A/C but all 3 are '70 or newer (see below)

The information I have states that the hot idle compensator valve is only fitted to '68 & '69 cars with A/C but the '70 & '71 cars all have it fitted(A/C or not)

This valve is a thermostatically operated air bleed, used to relieve an overrich condition at idle due to abnormal temperature.

"I have a '69 AVS, 4618S, and am wondering about a few things. This plug is supposed to cover an off idle adjustment screw, according to the FSM. Should I gain access to it for cleaning and adjustment?"

What is the build date of your carb/car?
I suspect it is quite an early '69 440 Auto, non air car.

The car was built on September 4, 1968. I found a J8 carb, so September '68 build on the carb was the best I could do.

I wouldn't remove the plug.

I'm sure I'll leave that one alone.

"This is where the idle limiter screws, as the FSM calls them, are located. They are covered by a plug and staked in. Should I gain access to them for the rebuild also?

Not unless you have to, test run the carb first & if it can be adjusted OK with the one screw, leave the plugs well alone.

The motor is stock except for the Edelbrock carb that I'm replacing with this, so I guess I'll leave the plugs and idle limiters alone since I'll still have some adjustment with the one on top.

I noticed your carb has a hose tail rather than the tube fitting, the Edelbrock fitting (adapter inverted flair part# 8090), in the carb you are using now will fit & work fine.

It is not identical but it fits & should do the trick, like the Carter fitting the Edelbrock one has a 3/4" hex although it is a bit (.177") longer, brass rather than steel (different colour) & is not counter bored for the factory style mesh filter although this could be easily done with a standard drill in a lathe or drillpress if required.

The carb looks quite tidy, how do the jets, rods, springs, pistons & throttle shafts look?

The carb looks good. I'm sure it was rebuilt before, but it doesn't look like they butchered it, other than the missing choke pieces and tag. The FSM says remove the jets. Should I? I don't see why I need to. How much clearance should there be on the pistons? One side is polished, so I'll see how out of round they are. That should tell me how much wear they have. The throttle shaft feels the same as the newer Edelbrock that's on the car now. I have the missing parts for the choke pull-off, but not the pull-off servo itself. I'll also need the choke. Why would someone think the original carb was better off in the garbage? This really bugs me.

Definately pull the jets. All kinds of crap can collect in the jet wells.

I have had problems sometimes removing them. A propane torch and some penetrant took care of that.

Holes threaded but no compensator.

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Yep,69 440 4spd .

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The best I can figure any of them that have all 3 started life with the single and someone added the lower 2 at a later date.

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I always thought is was a auto/4spd thing
Both my late 4426's have the single adjuster While my mid 68 4401 had two adjusters.

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Yea, I'm still trying to figure out exactly what the deal was on the adjusters, I can only go by used originals I've seen and the VERY few surviver cars I've seen with untouched carbs. I've had a couple pretty knowledgable people suggest that maybe all of the 68/69 carbs originally came with single adjuster but were later modified to have the 2 lower adjusters, however I've seen a fair number of double adjuster carbs that looked very correct and original, so I feel pretty certain they came both ways.

Exhibit "A"

Foot of the above carb

Scott,
The 4426 that's on my RR had a pink paint stripe across the E8 4426 on the base when I bought the car.
The car had been sitting for 20+ years and I needed to go throught the fuel system, when I soaked the carb I lost the stripe. Does the stripe have any meaning? Wish I had taken a pic before I soaked it, but didn't.
Sorry for going off the topic here, but just wanted to know.

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Wish I had taken a pic before I soaked it, but didn't.

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Me too, I've never seen one like that. Probably either an inspection mark or some kind of visiual aid to denote it's application.

4 speed carbs, I like the AVS much ,over a holley vacuum secondary for the street/strip.

heres the 4426 carb i picked up off e-bay a few years ago, plugs still in it, never removed. I had the pri shafts bushed, then rebuilt it, stuck it on the 383 RR which is near stock and tried to adjust the vac/idle, would not respond to the top screw didn't idle bad, but went with the 69 avs that was on the car. I'd bet the dealers removed the plugs on a lot of these carbs to tune them in better back in the day.

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I'd bet the dealers removed the plugs on a lot of these carbs to tune them in better back in the day.

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Quite possible

Ill be watching this thread as well....just picked up a 4640SA carb for my 69 440 with A/C. It has the 2 adjusting screws.

Got a vintage "Jiffy Kit" to rebuild it.

What does everyone do for the yellow cad plating on the rods? Eastwoods paint system or actually have them cad plated somewhere?

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What does everyone do for the yellow cad plating on the rods? Eastwoods paint system or actually have them cad plated somewhere?

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I use an outside plater, there are several colors involved in doing most carbs. Nothing else looks right IMO.

Here are some more pics. This is the port where the A/C equipped cars have that thermostatic air bleed that was on this carb, but the port wasn't drilled.





Here's the bottom:



I started with this:



I removed the plugs with these tools, turning by hand, and this is what came out:



I wish someone told me that the threads go all the way to the front of the carb. I thought the idle screws were smaller than the normal ones, and people tapped the holes for the bigger adjusters. Well, I didn't damage the threads, so all is good. I'll use the adjusters from the Edelbrock if they fit instead of the small ones.



As for that off idle adjuster--if I have problems, I'll just plug the hole.

I just re-used the stock mixture screws. They work just fine, you just need a long skinny straight blade screw driver to reach in there, not a big deal. I picked the lead plugs out of mine with some dental type metal picks.

If you use the bigger screws with the springs, they are less likely to self adjust.