Carter AFB lean at idle

[Jim914]

Have a Carter AFB. I can't richen up the idle circuit enough to get it to idle smooth. I can't find any vacuum leaks cleaned everything in the carb but nothing helps. Real good throttle response. Restricted with my hand and idles good.
Need something to look for. Thanks

 

[Don Frelier]

What is the timing at?
Retarded timing will make it act lean

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[AR67GTX]

Is it on a stock or modified engine? I thought cleaning carbs in good condition by blowing carb cleaners through all the passages was sufficient to clean bleeds of fuel deposits and Dragon Slayer suggested otherwise and recommended cleaning them with appropriate bit sizes from a micro drill bit set. i hit some resistance in most of the bleeds in a good looking set of Hemi carbs I had just rebuilt. if you have the carb off the car and apart it can’t hurt to clean (ream them out) as the idle bleeds do affect idle mixture control and richness.

 

[RJRENTON]

Is it on a stock or modified engine? I thought cleaning carbs in good condition by blowing carb cleaners through all the passages was sufficient to clean bleeds of fuel deposits and Dragon Slayer suggested otherwise and recommended cleaning them with appropriate bit sizes from a micro drill bit set. i hit some resistance in most of the bleeds in a good looking set of Hemi carbs I had just rebuilt. if you have the carb off the car and apart it can’t hurt to clean (ream them out) as the idle bleeds do affect idle mixture control and richness.

As stated, the primary booster venturii assemblies control the idle and off idle fuel feed circuits. When cleaning the primary booster venturii assemblies, use only a quality carb cleaner and compressed air. The idle fuel metering orifice usually is a 0.034" to 0.036" size, and can be increased slightly, to richen the mixture, but not recommended. The idle mixture AIR bleeds, if enlarged, will result in a LEANER mixture. On the back side of the booster venturii assemblies is a small brass orifice pressed in place. It can be soldered closed and re-drilled to slightly smaller orifice. This will result in a slightly richer mixture. Very difficult to perform but doable. If doing any drilling, use only number drills (in decimal sizes) and a hand held pin vice.
Just my opinion of course.
BOB RENTON

 

[rumblefish360]

Have a Carter AFB. I can't richen up the idle circuit enough to get it to idle smooth. I can't find any vacuum leaks cleaned everything in the carb but nothing helps. Real good throttle response. Restricted with my hand and idles good.
Need something to look for. Thanks

This is such a “In General” statement, I find it hard to believe anyone is actually trying to answer the question without knowing Jack about anything on what exactly you have.

How about some information like;
Carb size & model number
Jet & rod currently in the carb
Spacer used under the cars
What intKe
What head
What engine cid
What cam
Headers or not
OMGOOOOOOOOSSSHHHHHH the list goes on and on.

 

[Jim914]

I can understand you.
Well it's a stock 426 with a purple shaft. Carb is original to the motor. It's basically what came from the factory. Just a regular streetcar

 

[rumblefish360]

Oh my Lord….. good luck my friend. Good luck.

 

[RemCharger]

Uh, so it's got 2 afbs????
Which one is the bad one

 

[Geoff 2]

I think he means a 426 with single 4bbl. [ 1963-66].
Need more info. Engine stock? What happens when mixture screws turned in or out? Do they affect idle? Etc. Carb ben touched?

 

[Jim914]

Uh, so it's got 2 afbs????
Which one is the bad one

Just 1. Street wedge

 

[Dragon Slayer]

What is the AFB # on the ear of the carb? So you have good response despite a lean condition? Typically make sure float level is set correct, clean out idle ports on idle mixture screws and also between primary venture idle port through carb body to screws.

The cleaning out of the bleeds needs to be done knowing the stock values. I do recommend it, air bleeds, idle fuel bleed and IFR. Gets you to a base line. Most likely your idle fuel bleed (small tube on each of the primary venturis) is .035"

Also do not discount the gasket being damaged or wrong between venturis and body. Seen that before.

 

[AR67GTX]

Actually, a lot of people would like to have a slightly lean idle with good engine response. That means your transition circuit must be working well. Most posts on this subject are my carb is idling too rich and stinking up the place. I’m saying this a bit tongue in cheek. It doesn’t sound like your carb could be off much - probably just go through all the basics and make sure it’s clean and all adjustments are spot on. Check to make sure it’s sealing up to the intake and no vacuum leaks.

 

[toolmanmike]

Vacuum leak somewhere?

 

[Dave6T4]

I check for vacuum leaks with a propane torch. Open the valve on the torch a bit, but don't light it. Move the torch around the carb base, and along both sides of the intake. If you have power brakes, pinch off the vacuum hose to the booster. Wherever the idle speed increases, there is your vacuum leak.

 

[Jim914]

Aha think I sent problem 2 extra holes. Am i correct?
Don't remember seeing those

 

[RJRENTON]

Aha think I sent problem 2 extra holes. Am i correct?
Don't remember seeing those

View attachment 1292697

Those two holes, and sometimes on the secondaries, are vapor vents, used to vent the barrels during hot shut down soak. These are not your problem. Just my opinion of course.
BOB RENTON

 

[Jim914]

Well maybe not. I drug out another Carter and it has the same holes. There are holes on the secondaries also. What is the purpose of these holes?

 

[Jim914]

Those two holes, and sometimes on the secondaries, are vapor vents, used to vent the barrels during hot shut down soak. These are not your problem. Just my opinion of course.
BOB RENTON

Hey you know more than me. I will continue on.thanks

 

[Dragon Slayer]

As Bob said. They disappeared in 68 with the CAP emission carbs, when all venting was captured or meant to be captured. Is the choke pull off used? I see your not using ported vacuum for the distributor. Can you explain why you think it is lean?

 

[AR67GTX]

Oh my Lord….. good luck my friend. Good luck.

Even though it turned out not to be a Hemi I can’t help but chuckle at this. So true.