The Carter carburetor has been around for a very long time. The WCFB carburetor which came on some of the earliest Corvettes continued in production through the mid-'60s. Today the owner of a Carter carburetor can make some simple adjustments to achieve peak horsepower and performance.

Place the vehicle in "Park" or "Neutral," according to your transmission type. Apply the foot or hand brake.

carter avs carburetor

Raise the hood and disconnect the negative battery cable from the battery post. Use a socket to remove the top air cleaner housing bolt, or remove the butterfly nut by hand. Remove the housing. Refer to your Carter manual for the location of the linkage arms that connect to the top case air horn of the carburetor. Remove the hairpin retaining clip that attaches to the choke lever arm, using needle-nose pliers. The choke lever arm operates the the large choke valve in the top of the carburetor.

Use pliers to remove the clip that holds the accelerator pump rod to the pump linkage arm -- the accelerator pump plunger sits directly above it. Disconnect the fast idle rod right next to it, in the same fashion.

Be certain you know which pin connects which lever or rod. Loosen and remove all 10 air horn screws on the top of the carburetor, using a screwdriver.

Pull the air horn off and tip it upside-down so you can see the float mechanism. The two floats sit on a horizontal plane. Use a small ruler to measure the distance between the gasket surface of the air horn and the bottom of each float. Use needle-nose pliers to bend the innermost tang next to the float to adjust the height. Adjust both float tangs. Turn the air horn upside down and let the float hang -- this shows the float drop.

Use a small ruler to measure the distance from the bottom of the air horn gasket surface to the bottom of each float. To adjust the floats, use needle-nose pliers to bend the tangs on the outside of the hinge mechanism, either up or down. Place the air horn back onto the carburetor throttle bottle and insert the 10 mounting screws. Tighten the screws with a screwdriver. Reconnect the choke lever arm, accelerator pump rod and fast idle rod, in the same fashion you removed them.

Use needle-nose pliers to position the clips in place, in the same orientation as when you removed them.

carter avs carburetor

Connect the negative battery cable temporarily by hand. Look at the position of the choke valve at the top of the carburetor. For a cold engine, the valve should be closed. If not closed, loosen the three screws on the circular choke housing and turn the housing dial either clockwise or counterclockwise to open or close the choke valve. Close the valve very slowly by turning the housing dial until it just touches the carburetor throat sides. Tighten the three screws with a screwdriver.

AVS 4 Barrel

Start the engine and let it warm up to normal operating temperature. Watch to see if the choke valve opens completely. If not, loosen the choke housing screws and make a small turn of the dial to open the valve completely. Re-tighten the choke screws with a screwdriver. Shut the engine off.

Remove the vacuum line at the carburetor base. This line will route to the vacuum advance fitting on the distributor.Eldon, Missouri Carter produced 4 different styles of four-barrel carburetor. Each will be covered in some detail. Note that in no case does one type replace the previous type. Beginning inat least two different types were produced in all years through I am quite aware that Federal Mogul, after purchasing Carter, produced several models of clones of the AFB, and these also have been produced to be sold by other companies.

Many enthusiasts are still using, or trying to use these Carter carburetors today, often on non-original applications.

The two major mistakes made by the average enthusiast are: A starting with a carburetor, which is difficult to adapt to the specific application; and B believing that most parts within a given style of carburetor are interchangeable.

An example of A might be trying to install an AFB carburetor designed for a Chevrolet 8 cylinder onto a Pontiac 8 cylinder or vice versa.

The Chevrolet and the Pontiac engines have two entirely different fuel requirement curves. Often, when I suggest this to a novice, I am told by the novice that he is smart enough to change jets and metering rods, in which case I concede this point, and walk away. For example the Pontiac will want a significantly larger idle jet pressed-in than the Chevrolet. Yes, if one has the proper set of drills, and knows the correct size, one may drill out the idle jets.

But one must also consider air bleeds, idle restrictors, idle bypasses, and especially the secondary airvalve. The angle of attack of the airvalve is much greater for the Chevrolet engine than for the Pontiac engine. Trying to use the Chevrolet airvalve on the Pontiac will result in hesitation or bog when the secondary engages.

Can this be tuned? Certainly, if one has all of the specialized tools, parts, and the knowledge of which to use. We have found one has many fewer issues if one simply does a little homework and starts with a carburetor more or less designed for ones application. Many enthusiasts are disappointed to learn that very few original equipment carburetors have published CFM ratings, when in fact; most of them do not understand the meaning of CFM anyway.Cars by name Trucks and Jeeps. Carter Carburetor was established inand lived through Carter was popular through the years, particularly fromand took a position of honor on Chrysler vehicles over the years — not just on the pedestrian models, where two-barrel BBDs were common, but on the best cars Chrysler could make, Imperials and letter-cars.

Every Chrysler letter-car reportedly used Carter carburetors. The company started with William Carter, born in ; like many young men with mechanical ability, he started out in bicycles, opening a repair shop at the age of Inafter moving to St. Louis, he started experimenting with automobiles, discovering like many others that the carburetor was of supreme importance in keeping things going. He began to work with wooden molds, and eventually produced a cast brass carburetor of relatively high precision; it could meter and deliver fuel more accurately than many competing units.

How to Rebuild the Carter AVS Carb

According to HemmingsCarter may have created the downdraft design and the choke valve. It was a four story building on a ten acre site. They would keep it as a standalone company for 60 years. The result was the Carter Y-S carburetor model Swhich was later retrofit to other off-road vehicles.

Starting inJeep switched to the new YF single-barrel carburetors; inthe six-cylinder used the Carter WDG single-barrel. This was supplemented in by the Carter WC two-barrel. The company would rely on Carters through the s and into the s, keeping the YF for a surprisingly long time. Two of these were used on the Chrysler C, mounted atop the cubic-inch Hemi engine.

Dual WCFBs were also used on the similar Hemi in the B, and then on the famed cubic inch version used in the C and D as well as other Chrysler Corporation cars. In any case, the AFB was launched in ; it had a lower height than the WCFB, all major castings were aluminum, and the throttle body was cast with the main body. Originals were identified by a triangular, aluminum ID tag on one of the fuel bowl screws.

The AFB was well-designed for adjustments; the carburetor can remain on the car while the jets, floats, and metering rods are replaced, unlike similar Holleys, and both jets and metering rods are numbered, with the rods showing four digits — the first two for the normal diameter, the second two for the power diameter.

The piston, step-up rods, and springs could even be replaced without taking off the air horn. The system used a counterweighted air valve to slow the opening of the secondaries; it was effective but one could not adjust the time it took for the secondaries to open. The AVS was a better design on the street, and would later be brought back by Edelbrock. The historic Carter factory closed inalong with Carter itself.

Jeep continued to use the Carter BBD carburetor on its 4. Since the factory had closed, these carburetors must either have been built and stored, or produced by another supplier from the original molds.

The latter may be more likely, since various other Carter carburetors were later produced by Weber and Edelbrock. With the rise of electronic fuel injection, accelerating in the early s, carburetors became obsolete; even before then, Holley had been undercutting the company.

The last Carter carburetors were used by Chrysler in The BBS had already been replaced by Holleys in the early s. InHemmings announced that St. Mike Muenz visited the site on August 28, He wrote that Carter Carburetor Corporation in north St. These were taken with a HP Photosmart Spread the word via Facebook! We make no guarantees regarding validity or accuracy of information, predictions, or advice —.Carter carburetion and Mopars are synonymous. Performance Mopars from the musclecar years almost always came topped with a Carter to provide the fuel mix.

The AFB carb was conventional in the secondary circuit in that it used a conventional booster venturi configuration to deliver the secondary fuel flow. The secondary throttle plates were mechanically operated. In order to provide for a smooth transition into the secondary circuit without the benefit of a secondary accelerator pump circuita counterweighted velocity valve was installed above the throttle plates.

The velocity valve acted as an auxiliary to the throttling system, delaying the airflow through the secondaries until engine demand overcame the counterweight and allowed the valve to open.

The delay in airflow slowed the progression into the secondary circuit, allowing the airflow through the secondary booster venturi to start drawing fuel.

The goal was to provide enough of a delay in air flow to prevent a lean bog as secondary airflow is suddenly initiated by mashing open the throttle.

The system worked, but it had two flaws. First, the positioning of the velocity valve is above the throttle plate and below the discharge nozzles. Besides delaying airflow, this offers little help in initiating fuel flow through the booster. Second, the system was not readily adjustable to vary the opening rate. In contrast, the AVS carb--designated for its Air Valve Secondary--was quite a departure from convention at the time of its introduction.

The counterweighted velocity valve of the AFB was scrapped, and a spring-loaded air door was fitted at the top of the carb. Positioned above the fuel-discharge point, the air valve created a depression, or low-pressure area at the fuel-discharge point. This dramatically increased the reaction rate of the secondary fuel circuit.

The function of the AVS's air valve in drawing fuel flow was advantageous compared to the old AFB system's function of simply delaying airflow. The system was so effective that a conventional booster venturi wasn't needed, and AVS carbs were fitted with fuel spray bars, which complemented the air valve perfectly. To cap things off, the spring-loaded air door was easily adjustable for opening rate by simply loosening a lock screw and winding the spring tension on the valve's shaft.

And let's not forget the Magnum-equipped B- and E-Bodies from the peak of the glory days. In fact, take your pick of, and high-performance four-barrel engines, and with the exception of some s in '71, you'll find an AVS on top. We recently found a fine '70 AVS carb collecting dust on a salvage-yard shelf and had to have it. These carbs are remarkably rugged and easy to rebuild. Steve Dulcich photographer. Share on Facebook Share on Twitter.AFB's appeared in and were used as original equipment on most makes of car at one time or another up to Interestingly, some Ford AFB's weren't made of aluminum at all, and were in fact cast out of zinc.

Most parts, including tuning parts like the jets and metering rods are interchangeable between the original Carter AFB's and the currently produced Edelbrock carbs.

Whereas the AFB used a velocity valve, which is a counterweighted flap below the secondary venturi, the AVS used an air valve, which is a spring loaded flap above the venturi. The purpose of the two is similar, but the air valve is adjustable from outside the carb.

When the throttle is opened so that the secondary throttle plates begin to open, vacuum develops under the air valve, slowly pulling it open. In this way, the air flow is controlled and the mixture is kept from getting too lean if the throttle is opened suddenly. AVS carbs were found mostly on Mopar applications from Quality carburetor rebuild kits, choke pull offs, choke coils and floats for American carburetors.

Trademarks appearing on this site are the property of their respective owners. They appear here for identification purposes only. No endorsement by the trademark owners is to be construed. All prices are in US Dollars.Eldon, Missouri Accelerator pumps. Often the accelerator pump gets the blame for other problems.

It is very easy to test the function of the accelerator pump. Start the engine, and warm to normal operating temperature. Shut off the engine. Remove the air cleaner. The choke butterfly should be fully open, as the engine is warm. Observe the pump jet in the carburetor, and with your hand, work the carburetor throttle to the wide-open position. You should observe a healthy squirt of fuel from the pump jet.

carter avs carburetor

A single barrel carburetor will normally squirt a single stream; while a two or four barrel carburetor will normally squirt 2 streams.

If you see the stream s of fuel, the pump is working. It is important to start the engine prior to doing this test. With modern gasoline, it is quite possible the carburetor will be completely dry prior to starting. If there is no gasoline in the bowl, the pump will not work; and this would give a false result.

Bog, Hesitation, Stumble. This paragraph applies to an instantaneous bog, hesitation, or stumble upon acceleration. This paragraph also applies to relatively stock engines with the original carburetor. We will discuss two types of bog: the first is bog when the vehicle is accelerated from a stop; the second is bog when the vehicle is accelerated from cruise. Most modern carburetors are designed to function with roughly 0.

This clearance allows for maximum velocity of idle air past the idle ports. Exceptions to this are GM carburetors with the idle speed air screw, and end carburetors on tripower. Setting the idle for the highest vacuum idle reading will result in too little clearance of the throttle plate; forcing too much of the idle mixture through the lower idle port and too little through the idle transfer slot. When the throttle is opened, there is now sufficient velocity of air to sweep all these droplets into the cylinders, creating a mixture which is too rich to burn, hence the bog.

As soon as the overrich mixture is pumped out the tailpipe, and a normal mixture is ingested by the cylinders, the bog disappears. A defective advance mechanism can also cause bog; as can a defective accelerator pump. If bog exists only from an idle, not when accelerating from a constant speed, the idle adjustment is probably the culprit.

Bog from a cruise RPM may be caused by a defective advance mechanism, but on 4 barrel carburetors is often caused by the secondary side opening too soon. The Carter AFB uses weights, and therefore never goes out of adjustment.Note: Allpar does not take responsibility for the veracity of any information or opinions here, does not claim expertise, and is not responsible for any consequences.

Please proceed at your own risk. Cars by name Trucks and Jeeps. The Carter AVS almost perfectly hit the peak muscle car years, appearing atop Chrysler engines from to He also remembered that it was standard or optional on every V8 but thewhich was only sold in two-barrel form in those years.

It is generally thought of as a superior street carburetor, and was later brought back into production by Edelbrock. Inafter just a year in the field, all AVS carburetors for cars with air conditioners had hot idle compensators, to compensate for the high underhood temperatures these cars could endure when idling for a long time.

The compensator, placed between the secondary bores, brought extra air into the engine during hot idling. It was controlled by a bi-metal spring, placed on the side of the carburetor, with an adjusting screw that was not meant to be changed in the field. The default was blocking any air from going through the air passage; when it was active, the spring lifted a valve off its seat, and air went from the horn, through a passage, and directly into the intake manifold.

The company noted inas well, that primary throttle shafts in all four barrel carburetors for the Challenger and Barracuda were offset by 0. The secondaries are controlled by a spring loaded air door over the butterflys that looks a lot like a choke.

Turning it the other way can reduce hesitation stopping for a moment and then performing normally. Turning the flat-head screw one way increases the reaction time, the other way reduces it; the Torx screw locks the flat-head in place. We strive for accuracy but we are not necessarily experts or authorities on the subject.

Neither the author nor Allpar. By reading further, you release the author and Allpar, LLC from any liability. Spread the word via Facebook! We make no guarantees regarding validity or accuracy of information, predictions, or advice —. All rights reserved. More Mopar Car and Truck News.

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