How do you set the air and fuel mixture on a carburetor?

Answer 1

Idling or running? while you can adjust the idle mixture on most cars, you usually have to change the jets,to change the running mixture, that's what they mean by jetting the carb

Answer 2

There is an idle curb adjustment decal on the inside of the hood, usually on the frame in front of the radiator.
It shows the RPM setting, Idle Curb adjustment and Ignition Timing.
It is a must to have a tachometer. one wire goes to the coil positive side,looks like this,(+), the other wire goes to any good ground on the engine, but not attached to any part of the carb or battery connection Start the car and bring it to normal operating temperature. Check the ignition timing to be within the spec's. It is a good idea to spray the carburetor with carb cleaner inside and let idle for a few minutes, if the engine dies restart it.
Next the 2 mixture screws are located near the base of the carburetor facing toward the radiator, Sometimes they have factory plastic caps, remove them and set aside to be put back on afer adjusting. Make sure the choke is fully opened and all lights, A/C and other items that will effect the operation of the vehicle are off
Next back out each screw 1/8 turn at a time counterclockwise until the maximum idle speed is attained, checking the Tach to the decal RPM's. Once you set the screws, be careful when retuning the plastic caps to the screws that you don't change the speed. They should just push on to each screw. It is always good to do a tune up, changing spark plugs, wires, distributer car and rotor,as it will effect the smooth runnng of the engine, beforehand. Also check all vacuum lines for leaks going to the carb and to the intake manifold. You can check this by using some water squirting around the vacuum lines to any connections.
Once you have the air/fuel mixture adjusted , drive the car for a few miles 5 miles is ok. it should be ok, if not you must do it again adjusting. Note: If you don't have a Tach, purchase one at any auto parts store, a cheap simple one is ok.

Answer 3

Be more specific: Brand of carb. part number etc.
Most older carbs.
#1.Set the idel speed.
#2. have two idle mixture screws in the primary (front) barrels. With a portable tachometer or accurate vacuum gage hook it below the throttle plates and note the vacuum while the motor is at idle in park with the EM brake on. Very slowly screw one idle mixture screw in until the motor looses rpm's. Slowly rotate back out till you exceed the rpm you started with. Do the same steps to the other idle mixture screw. When you're finished it may be necessary to re-set your throttle idle speed screw.

If you suspect a horrible rich mixture and it's a Holley pull the fuel bowls and inspect the power valves the neoprene around the valve may have ruptured causing raw fuel to be pulled into the discharge ventures at idle.

Answer 4

Lookin @ the base of the crab.(assumin it is a four barrel, or even a two barrel) you will have two mixture screws on the front of the carb.(on the four barrel). Screw these in(leftie Lusy, rightie tightie) and then back 'em out one and a half turns to get the startin point. Which will require a CO2 meter on the exhaust pipe to do the fine tunin, beyond that.

But, I use to just ran it set @ the one and a half mark. Since, I did not have access to any type of metter for the measurement of the exhaust gases.

Good luck!