First, you need to keep in mind that the Autolite 2100 is basically the front half of the 4100, and as such the following questions and answers apply to both carbs.

What is Annular Fuel Discharge?

Many enthusiast consider the Autolite 2100 (2V) and 4100 (4V) carbs to be the best carb ever built. The engineering involved in their design is tremendous, specifically the “Annular Fuel Discharge”. This is state of the art technology was patented by Ford Motor Company in 1957. Therefore Autolite carburetor were the only carbs produced using this technique of metering, distributing, and mixing fuel into the air stream. While downleg boosters utilize a single orifice to discharge fuel, annular boosters employ a series of several smaller orifices, which instantly change the fuel from a liquid form to a gas vapor. And as you probably already know, it’s vapor that burns, not liquid.

At lower engine speeds, slow air speeds in the venturi's create a weak signal, which reduces the amount of fuel moving through the boosters. However annular discharge boosters offer multiple points for the fuel to enter the venturi, as opposed to a single discharge point. This yields measurable advantages, especially when large-volume carburetors are used in conjunction with a long-duration camshafts. Annular-discharge boosters can greatly improve throttle response and driveability, even when a weak manifold-vacuum signal is present at idle, partial throttle, or sudden acceleration.

Annular discharge carburetors produce greatly enhanced torque in the lower RPM range, more peak horsepower and torque, as well as better combustion and fuel burn throughout the entire RPM range. Which results in superior fuel economy, improved throttle response, and enhanced overall performance.

Why do Autolite Carbs require less maintenance and why are they safer to use?

Autolite carburetors will virtually run forever, or at least until dirt enters the carb. Due to its’ one piece base, there are no gaskets to dry out, crack, or leak fuel. Not only does this result in lower maintenance, it greatly improves the fire safety, especially when the carb sits directly over the exhaust headers, as is the case with our inline sixes.

Why should I pay more for an Autolite carburetor from Pony Carbs?

With their many years of experience rebuilding carburetors, Pony Carbs eventually learned how to re-calibrate Autolite carbs, making them better than a factory calibrated carb. Every carburetor is re-calibrated and adjusted to overcome the inherent carburetor problems that existed in OEM carbs, such as hesitations, flat spots under acceleration, and hard hot starting. They also re-calibrate the carb for today’s gasoline's, installing updated gaskets and parts whenever applicable. Every carburetor is completely disassembled, including the throttle shaft(s) and choke assembly. All pieces are soaked, media blasted, polished and/or re-plated when necessary. Once every part has been thoroughly cleaned and inspected, then re-assembled, tested, and adjusted by skilled technician on an actual running test motor. All carburetors come with new gaskets and fuel filter, timing and installation instructions, and an instructional video, and a full one year warranty (from date of shipment).

Is bigger really better, or a myth?

For years, people have had the notion that "bigger the better”. That concept is simply not true. What happens is that when too large a carburetor is installed, low end performance suffers without any appreciable gain in top end performance. An oversized carburetor will run “lean” off idle through the normal range operating range and then dump too much fuel at the top end, and run “rich”. A correctly sized (and functioning) carburetor will provide a constant air/fuel ratio through most of the operating range.

The idea is to choose a main body with a large enough bore and venturi area to allow maximum airflow through the carburetor and into the engine. At the same time, however, these areas must also be properly sized to promote a high-speed airflow signal into carburetor, a measurement of air speed that the carburetor reads in order to determine how much fuel to deliver to the incoming air stream. In theory, if the bore and venturi are too large, the signal will be weak at low engine speeds and the fuel will not be pulled from the carburetor's discharge ports accurately. The opposite of this effect is when the carburetor's bore and venturi are too small for the engine's airflow demands. While throttle response will be outstanding, the engine's maximum airflow, or power potential, will be diminished. The ideal carburetor sizing combination will be able to move the maximum amount of airflow through the carburetor while maintaining the strongest possible signal.

Therefore, it is very important to use a CFM calculator, thus ensuring you have selected the proper size carburetor for your CFM requirements. However, the calculated results are just that, calculated. Once you have done the calculations, consider the following "Rules of Thumb" before you make your final decision. Just remember, it's always better to start small.

How does the choke system work?

If you press the gas pedal all the way to the floor when the engine is cold (at whatever ambient air temperature), you are closing the choke plate on the carburetor. Once that is done, a couple of pumps of the gas pedal will provide the initial charge of fuel for the engine to start. Once the engine starts, a choke unloader will open the choke plate about 1/8”. From there, as the engine heats up, the fuel requirements continue to lessen (it can run on a leaner mixture). Heat produced either from a heat riser tube or from an electric choke cap will provide the heat to the bi-metal spring inside the black choke cap. As the spring gets hot, it unwinds and gradually opens the choke plate to a vertical position.

Do I need really a choke?

We have people from warm climates tell us all the time that they don’t need choke systems, however this is simply not true. Even though it may be 80 or 90 degrees outside in the morning, the cylinder walls, pistons and valves inside your engine are going to be the same temperature or even a little colder. When the engine is at full operating temperature it is approximately 600 degrees. The fuel requirements of a cold engine (90 degrees is cold compared to 600 degrees), are dramatically different than they will be when the engine is at operating temperature. In the first ten seconds of operation the engine needs twice as much fuel than when it is hot. For that reason, we like to use choke assemblies on all carburetors. When properly adjusted, an automatic (hot air) choke (especially an Autolite 2100 or 4100) will allow a carbureted vehicle run almost as well as fuel injection.

What is an Automatic or Hot Air Choke?

Hot air is provided by the heat riser tube connected to a sealed passage in the exhaust manifold. This is a SEALED passage, therefore there are no exhaust gases traveling through the choke tube. It allows cold air to enter one end of the exhaust manifold, get warmed up, and then pass through the insulated tube to choke cap on the carburetor. Again, the hot air will warm the bi-metal spring, it will unwind and open the choke plate. This process, at 40 degrees, will take 5-7 minutes. Which happens to be about how long it takes your engine to reach operating temperature. We like hot air chokes because the full opening of the choke plate corresponds with the time that it takes for an engine to reach operating temperature. When we receive requests for anything other than an automatic (hot air) choke, we often ask, “Why?” The answer is usually that the customer has removed the exhaust manifold and installed headers or HiPo exhaust manifolds. That is OK, you can still use an automatic choke. Instead of using the factory pre-bent stainless steel choke tubes that press into the exhaust manifold, we suggest using an extra long bendable insulated tube that clamps to the outside of the exhaust pipe. The open end of the tube will bring heated air up to the black choke cap in much the same way as the original tubes. You can bend this extra long choke tube to your specifications and it will look neat and factory installed. These tubes are available from Classic Inlines and can be ordered as an option.

What is an Electric Choke?

Electric choke assemblies differ from hot air chokes by the fact that the heat comes from the cap itself. Inside the black choke cap is a heating element, much like the heating element on your electric stove. It gets red hot and provides heat to the bi-metal spring to make the choke plate open. We do not prefer electric chokes because they go from closed to fully open in about 45 seconds. As stated earlier, it takes an engine 5-7 minutes to reach operating temperature, and in less than a minute the engine is not ready for such lean air/fuel mixtures that are going to be introduced into the engine. This causes drivability issues which include hesitations, flat spots, surging and dying. Anytime our clients will listen to us we try to discourage the use of electric chokes. The Ford electric choke caps that were first introduced in 1973 are unique. First, they operate on 7 volts, as opposed to the usual 12 volts. The 7 volts comes off a special terminal on a Ford alternator. In addition, they have ambient air temperature sensors built in and will not work below 60 degrees. Anyone who tries to use the original Ford electric caps alone will find they are pretty much useless. All of the Ford Motor Company vehicles 1973 and newer not only had the electric assist choke cap, but also had the hot air tubes running through the exhaust manifold. The idea was that the electric assist would open the choke cap at warm ambient temperatures when the engine didn't’t need much help (fully open in about 45 seconds). It was used mainly as an emission device, not a totally electric choke.

What is a Manual Choke?

If you spend enough time around older classic vehicles you will surely be familiar with the manual choke system. They consist of a knob and cable for the driver to be able to open and close the choke plate. These certainly have their place in trucks, farm equipment, lawn mowers and in some passenger cars. We do not like to see them used unless they were original to the vehicle. There are people that just prefer to be in CONTROL of the choke system and will install a manual choke for that reason alone. Manual choke conversions are really not a good option because of the unavailability of parts that are reliable enough to stay working. We very seldom do these types of conversions for that reason, except on high performance applications.

What is the difference between the 65-67 and the '68 Autolite 1100 carb?

1968 carburetors differ from the 65-67 in 2 ways. First, they do not have a spark control valve (looks like a power valve). For the engine to function properly with this carb, the distributor must have centrifuged advance (spring loaded weights inside) along with the vacuum advance unit. 1967 and older engines (except '66 and '67 California Emissions) utilized the Load-O-matic distributor, which had vacuum advance only. The second difference is the CFM. In 1968 Ford put a 170 CID size carburetor on a 200 CID engine. If you ever looked at the engine specs, in 1968 the 200 CID engine is rated at 115 HP (this was generous, it is probably more like 105 HP). The 1967 and older engines were rated 120 HP. By changing the venturi inside the 1968 carb to the larger 1967 and older size, we can substantially increase your performance. The difference in the standing quarter mile is about 6 MPH. The cost for this upgrade is $30.

What is a 480cfm-4V Spreadbore?

Focusing in on the 4100, there were 2 sizes manufactured (really 3, but you will never see a 1958 only 1.19). The most common 1.12" venturi 600 CFM, and the much rarer 1.08" 480 CFM, are the ones you will come across. The large 600 CFM (1.12) was factory installed on Galaxies and T-Birds with 352, 390 and 428 engines. The small 1.08 was used on "A" and "D" code 289's and 1966 only Galaxie and T-Bird's with 390 and 428 applications. (The big blocks used the small carburetor for emissions reasons.) The problem with this is that many enthusiasts "listened" to the rave reviews of this engineering masterpiece and the supply of 1.08's was been gobbled up. Just try to find one at a swap meet!

However, Pony Carburetors recently introduced a 1.12 venturi 4100 that works even better than the 1.08, especially on a performance inline six with the new aluminum cylinder head. By narrowing the primary venturi diameter to 1.00", it is now possible to get improved fuel economy, sizzling performance, and enhanced driveability that begins to approach that of fuel injection. With the small primaries (1.00") and the large secondaries (1.12") the Autolite 480cfm now has the spreadbore characteristics that were so desirable and utilized by several carburetor manufacturers in the late 60's and throughout the 70's. The end result of a spreadbore design maximizes fuel efficiency while maintaining neck jarring acceleration when the situation arises. Another wonderful thing out this spreadbore is that it can be used on the regular square bore intakes, as all four holes are the same size. It is a spreadbore, but only INTERNALLY. It is perfect for use with our new aluminum head and removable alloy intake manifold. Classic Inlines was shocked at the results we obtained when we went to Pony Carb's facility to do some dyno testing using a customers 66 Mustang with a performance inline six and our new aluminum head. To view the results, and see a couple of video's, please read our article on Dyno Testing the 480cfm speadbore.

Why am I having problems adjusting my new carburetor?

The timing is very important because the factory timing specs are just too retarded to get anything done. The engine really wakes up when you advance the timing correctly. Most of the problems that you are experiencing are probably due to late timing. "The number one problem in the industry concerning engine drivability is ignition timing . Timing lights do not work -the reason is; timing marks are located on your harmonic balancer. The harmonic balancer is mounted in rubber and over the years they MOVE.

Whenever our clients call us concerning drivability problems (hesitation, flat spots, surges) 99% of the time, the problem is ignition timing. We will share with you an accumulation of many years of experience and if you follow our GOOF PROOF method -you will be rewarded with the best drivability and performance you have ever experienced.

All Ford engines will run better, deliver more power, and give better fuel economy with the timing advanced BEYOND factory specifications. Premium unleaded fuel is recommended, especially in six cylinder engines. After you have read the procedure, your engine will perform the best when the engine will either just barely "ping" on full acceleration or not quite "ping." (PINGING indicates timing advanced too far.)"

For your engine to run properly the carburetor must be of the correct size. Ford manufactured 3 sizes of the 4100-4V and 8 of the 2100-2V carbs.