Carter Carb 3855 vs 3856

[Polara_500_Jr]

Anyone know the difference and if I can get away using a 3856?
The carb for dad's car is missing. I found a 3856, which is 65 383 Auto trans, this one is a 4 speed, so it should have a 3855.

The debate is whether I rebuild the 3856 to install, or just go buy a new Edelbrock carb and not mess with it.

 

[69chrysler300vert]

It is probably just a number difference. It should be fine to use. Granted my knowledge is only with holleys.

 

[GOLDMYN]

Just my $.02, they have different part# for a reason, buy a edelbrock and in the meantime, get the original rebuild.

 

[413]

Get that original 3856 carb and have it rebuilt. The auto and 4 speeds have minor differences but look the same.

The edelbrock won't run the same, it's a generic replacement, with choke and linkage connection difficulties.

 

[58Special]

I've got the same situation Rebuilding a AFB 4326S (Manal trans) that was installed on my Dads car.
Automatic trans was AFB4327S

 

[CBODY67]

They were different numbers for a reason, BUT that reason might not amount to anything in real world performance. Something that the engineers felt was needed, for whatever reason, might be the size of the "Low Speed Jet" in the bottom of the idle circuit feed tubes, for example, or a slightly-leaner idle calibration, but nothing that can't be worked-around. Might be something that only shows up on meters rather than in rear tire movements.

The Edelbrock probably has a more -evolved venturi contour for a bit finer fuel control, but also moves past the purpose-calibrated OEM calibration into a "wide-brush" world of aftermarket carburetors. Where such very fine distinctions are not significant.

You might match the Edelbrock's tuning to the OEM tuning of the carbs you have. As to metering rods, jets, and power valve springs. It might well be that the Edelbrock is pretty much "already there".

An AVS2 might be a better choice than an AFB?

Just some thoughts,
CBODY67

 

[Polara_500_Jr]

I am only looking as the original carb is missing. My assumption is dad sent it to someone to rebuild before he got sick and then passed. Who that might be, no clue. Not a lot of chance to figure that out either. That would have been ideal as he had it tuned for this engine/build.

I am going to rebuild the AT one for now. maybe look at getting an AVS Edelbrock in the future, or finding the original model carter used to rebuild.

We'll know if she starts/runs on Saturday I hope. After 4+ years apart, and reassembly like a jigsaw puzzle I didn't take apart it could be challenging.

@HWYCRZR is going to assist then as he did with the clutch/shifter installations, so let's hope!

 

[MoPar~Man]

What is different betw manual & automatic carbs

www.vintage-mustang.com

"The general rule of thumb is that a car with an automatic transmission uses a carb with vacuum actuated secondaries and a manual trans uses a carb with mechanically operated secondaries (meaning linkage is used to trigger open the secondaries). Also, on a carb used with an auto trans, there is almost always a "kickdown" linkage of some sort which downshifts the trans when the throttle is wide open. The latter generally takes the form of a pretty stout bent hollow rod which physically ties to the trans lever and the carb linkage at the carb. There is nothing "wrong" per se with using a carb with vacuum secondaries on a car with a manual trans. although the kickdown rod is eliminated."

 

[413]

Carter AFB carbs all have linkage opening the secondaries and and a weighted air valve just above the secondaries. Look inside it's there. Now some drag racers take that weighted valve out of the carb.

 

[CBODY67]

The AFB that came OEM on my '67 Newport 383 4bbl has no weighted air valve in the secondaries. All that is in the secondary side are the throttle plates themselves. Full mechanical operation. Not sure "why" it has nothing there, just that it does.

When I bought the car in 1981, with about 85K miles on it, it was completely unmolested by anybody. The carb number matched what was in the FSM as to numbers and such.

In an old Hot Rod Annual, from the earlier 1960s, it noted that on the AFBs with the weighted "air valves", to get the valves to open quicker it was common to file the weights to make them lighter. Might have been some rhyme and reason to end up with the heavier portions on a particular side to enhance the desired quickness?

Enjoy!
CBODY67

 

[LocuMob]

linkage connection difficulties

The #1481 adapter makes that a breeze.

 

[Just Carbs]

The #1481 adapter makes that a breeze.

Giving up the chock stove might be a concern.
The electric choke and 1481 adaptor do add to the cost.

 

[LocuMob]

Giving up the chock stove might be a concern.
The electric choke and 1481 adaptor do add to the cost.

I'm usually ordering a bunch of parts, so the $18 doesn't make much of an impact. Losing the choke can be an issue for some people.

 

[3175375]

Carter AFB carbs all have linkage opening the secondaries and and a weighted air valve just above the secondaries. Look inside it's there. Now some drag racers take that weighted valve out of the carb.

Some Carter AFB carbs all have linkage opening the secondaries and and a weighted air valve just above the secondaries. Look inside it's there. Now some drag racers take that weighted valve out of the carb.

I had a 57 New Yorker that had an automatic transmission and a 4 barrel carb with mechanical secondaries, bone stock.

 

[300George]

AFB (Aluminum Four Barrel) all had mechanical secondaries. AVS (Air Velocity/Valve Secondaries) same mechanical secondaries. Just had the weighted "air valve" above secondary throttle plates. Same idea the ThermoQuads had with the spring loaded plate. All to allow when the larger secondaries open, reduce/eliminate any "bog". When set up right, they work well.

 

[cudamark]

Build your 3856 and don't worry about it. It will work fine, or, at least as good and any other stock carb you choose. With any engine rebuild or changes and todays' fuel, even the stock 3855 would probably need some tweaks to get it perfect.

 

[Polara_500_Jr]

Build your 3856 and don't worry about it. It will work fine, or, at least as good and any other stock carb you choose. With any engine rebuild or changes and todays' fuel, even the stock 3855 would probably need some tweaks to get it perfect.

The Carter ended up being unsalvageable. I picked up an edelbrock avs2

 

[Polara_500_Jr]

edelbrock installed. avs2 1913, electric choke already on it.

We installed it and as soon as the fuel got the the carb she lit right up and pretty much purred. Didn't have the 21481 adapter so it's all waiting on that for some final tuning but it's running and idling well before that!.

So close, and y'all have been a huge help. both the local, semi local and internet only guys here.

If all goes well, this Sunday I'll share some pics of her driving off the lift for the first time since 2017!!!