When an owner decides to keep the Ford 6-cylinder Engine, the next decision is whether to keep it stock or upgrade for better drivability and performance. If a part needs to be replaced, sometimes it might not cost any more to upgrade than it would to replace with new, stock parts.

As it turns out with the Ford small six, upgraded parts generally cost more than stock replacements, and sometimes they cost substantially more. However, a lot of the stock parts are either very performance restrictive or only available as remanufactured units. 

Remanufactured parts (especially carburetors and distributors) are typically inexpensive alternatives to new replacement parts—that’s if the replacements are available as remanufactured units at all. The major concern that most rebuilders have with remanufactured parts is the chance that the body of the part, which almost always is a reconditioned original, can have deficiencies in the original design, or more typically, warpage or other dimensional issues that are difficult to detect and repair during the remanufacturing process. Many issues show up once the part has been installed on the car and has been in use for some time. 

The carburetor top (where it screws to the main housing) is the easiest part to envision this on. A warped top can cause easily detected issues, such as vacuum or fuel leaks, or more subtle issues, such as making the float difficult to properly adjust for proper performance. 

Fortunately, there are parts available to replace many of the original parts that will improve the starting and drivability of the car while vastly improving the performance.

The best reason to upgrade parts on your engine, and the easiest way to make the decision, is if an original part is malfunctioning. Other than worn-out internal engine parts, the most common sources of drivability problems are the carburetor and distributor. An issue on older engines with the Autolite 1100 1-barrel carburetor is that the housing can warp, leading to fuel or vacuum leaks.

AIR INTAKE

The nice thing about upgrades to the air-intake system is that you normally receive the added bonus of a visual upgrade as well. As attractive as a stamped-steel, painted enclosure with a snorkel on it is, most people want to upgrade the air cleaner because it is such a visible part of the engine.

The open-element air filter is a classic design that improves airflow to the carburetor. The increased surface area allows more airflow than the design of most OEM air cleaners. Whether or not it is a stock engine with a 1-barrel carburetor that needs more air is beside the point. They just look good.

Open-element, chrome air cleaners not only look good but also increase the amount of air that the engine can take in. They do this by eliminating the literal bottle-neck created in many factory air cleaners by the small-diameter snorkel. Most engines do not need the amount of air that can be drawn in through one of these filters, but unlike some other engine systems, the engine will only use the air it needs. 

 
If you have an Autolite 1100 carburetor, Vintage Inlines sells air-cleaner adapters that allow you to install most aftermarket air cleaners with a 5.⁄8 -inch base. The adapter was designed to not interfere with the choke linkage.

The drawback to open-element filters is that they sit on top of the engine where the air is usually hot. We all learned in science class that hot air is not as dense as cool air. This means that there are not as many oxygen molecules in the same volume (amount) of air. Of all the elements in air, the only one that the engine needs to burn fuel is oxygen. Less dense air means less oxygen to the engine. 

For some time now, remote air intakes (RAIs) have been popular. They gained popularity when import cars with 4-cylinder engines became popular with young drivers and street racers. From a practical standpoint, moving the air filter to a cooler part or outside of the engine compartment provides cooler air that improves performance.

For decades, racers addressed this fact of science by attaching hoses to the air-cleaner housing and drawing air from somewhere besides the hot engine compartment. This setup is known as a remote-air intake system or sometimes a cold-air intake. It is important to keep in mind that to be a cold-air intake, the relatively cool air must come from outside the engine compartment. A remote-air intake may consist of tubing that moves the air-filter element to a part of the engine compartment that is not as hot as the rest. 

On an inline 6-cylinder, it is not hard to imagine that the engine compartment on the opposite side of the exhaust manifold is cooler. Cooler is a relative term, but any decrease in temperature helps.

This Tech Tip is from the full book, FORD INLINE SIX: HOW TO REBUILD AND MODIFY. For a comprehensive guide on this entire subject you can visit this link:

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CARBURETOR & FUEL INJECTION

 The next part of the engine that we come to after the air intake is the carburetor. The carburetor has one main function: provide the correct mixture of fuel and air to the engine in all operating conditions. The gadgets and compromises involved in doing this are why carburetors look so complicated. They are also why engineers began using electronically controlled fuel injection on new cars as soon as it was feasible. 

The three types of choke systems used on most American cars were manual, hot air, and electric. Manual chokes used a cable routed inside the car for the driver to actively close and open the choke. Hot-air chokes use heated air from the exhaust manifold drawn through the choke housing by a slight vacuum.

The first adjustment that the carburetor has to make when you start the engine is to provide much more fuel than is actually needed to run the engine. It needs to do this because the atomized fuel mixture tends to turn back into a liquid as it contacts the cool inner surfaces of  the intake manifold or the intake log. In the case of the Ford small six, it has an intake log. The carburetor has a Choke valve that closes, restricting airflow, which makes the fuel mixture richer (having a higher ratio of fuel than air). In this way, the carburetor supplies enough fuel and air to the cylinders to allow combustion when the engine is cold. As the engine warms up, the choke valve opens and allows the air/fuel mixture to lean out some. Lean means there is relatively more air in the mixture.

For efficient combustion under normal driving conditions, the engine requires almost 15 parts of air to 1 part of fuel. This air/fuel ratio can be much richer during start-up. 

Hot Air Choke Assembly

The first carburetors on Ford small sixes used a hot-air choke assembly. The carburetor had a vacuum passage to the choke housing. This slight vacuum pulled hot air through a tube from a location on the exhaust manifold. It is important to note that it did not pull exhaust fumes into the choke housing. Because exhaust gases are corrosive, the choke components would not last long. The tube passed through the manifold and allowed air to be heated before it reached the choke. As the engine heats up, the air gets hotter and causes the clock spring in the choke to turn and move the choke plate lever. Hot-air chokes were barely adequate when new.

Electric Choke

In the 1960s, electric chokes began to gain favor, and most carburetors had an electric choke by the end of the decade. The electric choke operates by

sending current through the spring, which heats it up. As it changes temperature, the spring tightens or loosens and opens the choke plate just like the hot-air choke did. The difference is that the electric choke will be much more reliable because the operation does not depend on the presence of heated air from the hot-air tube.

Conversions

The aftermarket and carburetor manufacturers have developed a line of electric choke conversion kits for many carburetors that originally had manual, cable-operated choke assemblies. Much less common are kits to convert hot-air chokes to electric. There is at least one option for the Autolite 1100 common on Mustangs, Falcons, and other 6-cylinder Fords built in the 1960s. Vintage Inlines sells a billet aluminum, electric choke conversion for owners who wish to keep their original-style carburetor. While there is no performance improvement when converting to an electric choke, drivers will notice the consistency when starting and as the engine warms up when compared to a hot-air choke.  

Upgrading the carburetor to a later, larger version of a 1V carburetor improves starting, as most later-model carburetors were equipped with electric chokes, and performance is generally improved due to the larger size and/or newer technology. Going backward by installing an earlier carburetor is generally not recommended for these same reasons. A smaller carb with a hot-air choke is not an upgrade. 

Carburetors from 1969 and on had a bolt spacing of 3.⁄8  inches and require an adapter when they are installed on a small log head. Carburetors on small log heads had a bolt spacing of 25 ⁄8  inches. Because of this difference, an adapter is needed to put the larger-base carburetors on a small log intake. These adapters are commercially available, and well-engineered versions keep the proper orientation of the carburetor to the intake. Proper orientation generally allows the use of the original carburetor linkage. Holley 1946 carburetors from the late 1970s require conversion to a throttle cable when installed on earlier model vehicles.

Fuel Injection

 While not exactly new, bolt-on throttle bottle fuel injection systems are fairly new to the Ford 6-cylinder engine scene. The 2V adapters available

for the small six make it possible to bolt one of the new 2V systems to the integral intake manifold either with a 2V to 1V adapter or preferably by using a conversion adapter to get the most benefit from the swap. Two manufacturers are getting the most attention at the time of this writing, but do your own research and talk to owners who have made the swap for their opinions. 

Distributor

 On engines in vehicles built before 1968, the distributor was a unique design that did not have a centrifugal or mechanical advance. It instead relied on a modified vacuum signal from an SCV on the carburetor. This distributor was known as the Load-O-Matic and had no redeeming performance qualities. When a carburetor is replaced with a non-SCV upgrade, the Load-O-Matic distributor will provide even worse performance than before. The answer is to upgrade the distributor as well.

The first electronic distributor offered by Ford was the Duraspark, which was introduced in 1973. It used a control module and an electronic pickup to provide true electronic control of the coil operation. The Duraspark still used a vacuum advance to control timing advance. The Duraspark had a small-diameter distributor cap that led to the potential of spark jumping inside the cap due to the high voltage generated by the system.

For builders who want more reliability from their original distributor, there are electronic conversion kits that allow you to replace the original points. The most well-known is the Ignitor from Pertronix. It is important to remember that while the electronic conversion requires no maintenance and provides a much more stable pickup signal, it does not upgrade the voltage output of the original distributor by any noticeable amount.

To get better performance and stay on budget, there are a few Ford original equipment options that can be salvaged from the junkyard or purchased as remanufactured units from your local auto parts store. The easiest swap for a Load-O-Matic is the distributor from a 1968–1972 vehicle. These distributors use an unmodified vacuum signal and, more importantly, have a centrifugal advance feature.

Duraspark

They are still triggered by points and have a condenser, so while it is an easy swap, there are better choices. Starting in 1973, Ford used an electronic distributor known as the Duraspark. The Duraspark was all electronic, which means that there were no points to wear out or adjust. This upgrade requires the correct coil, the electronic control module (normally mounted to the inner fender), and the wiring harness to connect the components.

When searching for a donor vehicle, you must make sure all of the components are there, including the spark plug wires, although you will probably replace or upgrade them. A good rule of thumb is to take as many related or attached parts as you can get, including attaching hardware and brackets.

Duraspark II

In 1975, Ford updated the Duraspark with the most visible difference being the large-diameter distributor cap. Due to the increased voltage of which the distributor was capable, Ford found it necessary to use a larger cap to reduce the possibility of the spark jumping inside the cap from one post to the next. This problem leads to misfires that affect performance and can be felt while driving.

The new, improved distributor was known as the Duraspark II and was the last factory upgrade to the small-six ignition system. Because they were put on more vehicles in the 1970s and early 1980s, the Duraspark II is a better and more plentiful choice than the original Duraspark.

If this sounds like a lot of work to get used parts, and it kind of is, but it is the least expensive way for builders on a budget. If there are problems, the individual components can be replaced with parts available through local auto parts stores or online parts suppliers. 

Aftermarket Distributors

Over the years, there have also been aftermarket choices. In the 1960s, Mallory made a high-performance dual-point distributor, and Unilite later offered an electronic replacement. Both are very rare now, and replacement parts to rebuild a worn-out original are almost impossible to find. While both of these choices offered significant power and drivability improvements, the real improvements have come more recently with offerings that produce 50,000 volts or more. They can also be tuned by a process called recurving that matches the amount of ignition advance and, when it happens, to the modifications of the engine. Recurving has always been an option, but it is most effective when using a high-performance distributor. 

Performance Distributors 

A company called Performance Distributors in Memphis, Tennessee, has been very helpful to the Ford small-six engine community. Over the past few years, it has been willing to develop ignition products for these engines that other companies would not. These products allow engine builders to take full advantage of other performance upgrades. Along with a performance-modified version of the Duraspark II that features a full-length bronze bushing,

Performance Distributors offers high-performance control modules and coils to complete the Duraspark II package. 

From Performance Distributors is the Davis Unified Ignition (DUI) distributor. Based on the General Motors HEI distributor, Performance Distributors produces distributors for many engines, including the Ford small six. The Performance Distributors DUI is also available for the 144- and 170-ci versions and is the only electronic distributor made for these engines.

This allows car owners who want to upgrade and still keep their cars “all Ford” to do so. For owners who are okay with putting other parts on their cars, Performance Distributors also sells a distributor called the Davis Unified Ignition (DUI). The DUI is based on the HEI-type distributor from General Motors. The most recognizable feature of the HEI-type distributor is the cap, which contains the control module and the coil. This feature makes the DUI a desirable upgrade because you do not need to worry about wiring harnesses or where you are going to mount the control module.

The other feature that makes HEI-type distributors so popular is the one-wire hook-up. It literally requires one wire, a clean 12-volt signal in start and run mode, to power the distributor. All other functions are controlled internally. There is another connection on the distributor that makes it very easy to connect an aftermarket tachometer, including the reproduction Rally-Pacs for early Mustangs. 

These distributors, like the performance Duraspark II, are capable of producing over 50,000 volts. This level of spark is necessary to produce the most possible power from the small-six Ford engines. It also makes the car easier to start and helps with many drivability issues. Most experts agree that many symptoms on the 1960–1967 small sixes with the Load-O-Matic distributor that are first thought to be carburetor related can be solved by upgrading the distributor. If you choose to upgrade the distributor, you have chosen wisely!

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