The Ford Model A engine – primarily developed for the popular Ford Model A automobile (1927–1931, 4.8 million built) – was one of the most mass-produced automobile engines of the 1920s and 1930s, widely used in automobiles, trucks, tractors, and a wide variety of other vehicles and machinery."TK-3 and TKS", Tank Encyclopedia, The Online Tank Museum, retrieved November 27, 2022"Pietenpol Sky Scout", Western Antique Aeroplane and Automobile Museum (WAAAM), retrieved November 27, 2022
A four-cylinder, carbureted, gasoline-fueled, piston engine, derived from the Ford Model T engine, the Ford Model A engine – with a bigger bore and stroke, and higher compression ratio – was twice as powerful as the Model T engine."Model A Primer", Model A Restorers Club (MARC), retrieved December 6, 2022 Some derivatives, with improvements, were produced until 1958.Burtz, Terry: "Evolution of the Model A Ford Engine," Re-Engineering the Model A Engine, retrieved November 7, 2022 Tens of thousands of the original design remain active even in the 21st century.Davisson, Budd (engineer): "A Modern Model A Motor: Back to the Future," January 2022, Sport Aviation, Experimental Aircraft Association (EAA), duplicated at Static1.SquareSpace.com, retrieved November 30, 2022"History: Model A Ford Is 70 Years Old," May 15, 1998, The Auto Channel, retrieved December 8, 2022
Design and development Development and production history The Ford Model A engine was an evolution of the Ford Model T engine, but with double the power. It was developed in secret at Ford's Rouge Plant, in Michigan, and unveiled – with the Ford Model A automobile – December 2, 1927. The first Model A engine was completed earlier, October 20, 1927, and eventually installed in a 1928 Model A Fordor sedan, which Henry Ford gave to his friend, inventor Thomas A. Edison. There was immediate market demand for the Model A, but by January 1, 1928, just 5,275 Model A engines had been built – some not yet installed in a chassis, let alone shipped to a dealer."Ford History," Model A Ford Club of America, retrieved December 8, 2022"The 40 Horse Block - Evolution of the A-6015," Steve Plucker Ford Model A Research Project, retrieved December 8, 2022
However, by February 1929, production of the engines reached 1,000,000 units. At the end of Model A production in March 1932, 4,849,340 Model As had been built. (Several hundred thousand Model AA trucks had also been built, typically with the same Model A engine.) Model A historian Steve Plucker, using Ford company records, calculates that 4,830,806 production engines were built between October 1927 and November 1931.
All Model A engines built in the U.S. were built in the Rouge plant, however some were built at Ford plants in Canada and Europe. During that time, the Model A and AA engine cylinder block (part number A-6010), went through various external and internal changes.
The Model A was replaced by the 1932 Ford Model B, with an updated 4-cylinder engine, and by the 1932 Ford Model 18, with its new Ford V8 engine.
Basic design and characteristics
Like the Model T engine, the Model A engine was a water-cooled L-head inline-four (four vertical cylinders in line), "cast-en-bloc"-type piston engine. It had a displacement of (compared to the Model T's ).
This engine provides (brake horsepower"Engine" (specifications and illustration), Model A Garage, Inc., retrieved December 2, 2022) at 2,200 RPM – but at 1,000 RPM produces substantially more torque: . SAE-rated horsepower is 24.03, and compression ratio is 4.22:1.
The cylinder bore and piston stroke were also enlarged from the original Model T engine; they measured . Cylinder firing order is 1-2-4-3.
The engine has a 5-quart oil capacity. The crankcase is filled through an engine fill/breather tube mounted on the engine's left side. Modern 10W30 oils are recommended for newly rebuilt engines."Engine Break-in Instructions," Model A Garage, Inc., retrieved December 2, 2022 The recommended oil change interval is 500 miles.
Comparison to modern designs
The Model A's engine has three main bearings (versus five found in modern 4-cylinder engines), and they are smaller diameter, and longer, than bearings in a modern engine. The bearings are poured babbitt bearings, rather than modern replaceable insert bearings.Burtz, Terry: "Differences between Model A and modern design practices," Re-Engineering the Model A Engine, retrieved November 7, 2022"Block" , updated October 29, 2022, "Engine," Technical Q&A, Model A Ford Club of America, Inc. (MAFCA), retrieved November 7, 2022
Rather than a full pressure oil system typical of a modern engine, the Model A engine's oil system lubricates the main bearings by gravity feed, and lubricates the piston connecting rods by them dipping into the oil during motion.
A Model A engine has no crankshaft counterweights. There are no cam bearings. The Model A engine lacks valve seats, versus steel ring seats typical in a modern engine. The engine has a rather restricted intake port design, as compared to a modern engine.
Equipment, accessories, and drivetrain Intake, injection, and fuel
Normally, the Model A engine was supplied with a Zenith one-barrel, up-draft, float-type carburetor, which was gravity-fed from a tank in the engine cowl (between firewall and dash)."Other Carbs" / "Model B Carburetor," Model-A.org, retrieved November 30, 2022 The carburetor underwent many modifications during its relatively short (four-year) production run."How the Carburetor Design Evolved," Model-A.org, retrieved November 30, 2022
The Zenith has features, advanced for that era, that solved some early engine performance problems. The carburetor is designed to run lean, to allow for high-altitude driving. To allow better performance at low altitudes, and in cold weather, the fuel/air mixture ratio is controlled by a manual choke and "Gas Adjusting Valve" (GAV). To ensure adequate fuel flow during starting or acceleration, a secondary well momentarily provides an extra supply of fuel."How the (Zenith) carburetor basically works," Model-A.org, retrieved November 30, 2022 A manual fuel shut-off valve is also supplied, and some also have a manual throttle.
Although the Zenith Model A carburetor was fitted to the engines in the vast majority of Ford Model A cars (reportedly to 3.5 million of the approximately 4.8 million builtH Eugene Weiss. Chrysler, Ford, Durant and Sloan: Founding Giants of the American Automotive ..., Jefferson: McFarland, 2003 ), it was not the only carburetor used. Another 19 brands were fitted to various Model A engines – either as original equipment or aftermarket retrofits – and some Model A engines were retrofitted with the slightly larger, more sophisticated Zenith designed for the Ford Model B engine.
The engine works with modern unleaded regular gasoline.
In rare instances, the Model A engine has been powered by wood gas, produced in a wood gas generator, such as a "Gazogene," typically a large, sealed, stove-like cylinder mounted on the vehicle, or towed, which heated or burned wood (or charcoal), to produce fumes of flammable wood gas, as a minimal substitute for gasoline. The resulting gas was routed to the engine's intake manifold, via a duct and special induction system."1929 Ford Model A Gazogene Conversion," Tampa Bay Automobile Museum, retrieved December 6, 2022"Ford Model A drives on wood gas" (video of system and operation), Holzvergaser on YouTube, retrieved December 6, 2022Glon, Ronan: "From gasoline to gasification, or why we don't power cars with wood today," January 22, 2017, Hemmings Motor News (system fueling a Ford Model A engine is depicted and described), retrieved December 6, 2022
Engine electrical system The electrical system supporting the engine typically consisted of a 6-volt battery, a 6-volt DC generator (driven by a belt connected to the crankshaft pulley), starter, lights, ammeter, and ignition system (ignition coil, distributor, spark plugs) with connecting wires. A manual spark lever advances or retards the ignition, particularly retarding the spark plug ignition during engine starting."Electrical," , updated August 8, 2022, Technical Q&A, Model A Ford Club of America, Inc. (MAFCA), retrieved November 7, 2022"Electrical" (specifications and schematic diagram), Model A Garage, Inc., retrieved December 2, 2022"Ignition" (specifications, description and schematic diagrams) Model A Garage, Inc., retrieved December 2, 2022
The Model A was configured with a positive-ground system (positive battery terminal connected to vehicle frame and engine block) – opposite of the norm in modern "negative-ground" vehicles, often causing technical confusion.
Engine cooling system The Model A engine uses a centrifugal water pump, mounted to the engine cylinder head, and it works with the engine fan. The Model A engine uses plain water to cool the engine; antifreeze coolant is not recommended because the original Model A radiator is not a pressurized system. The pump circulates radiator-cooled water into the lower engine, and as the water becomes heated in the block's water jacket, it is forced out of the water jacket through the upper radiator hose, and back into the radiator, where it cools, and settles, and the cycle repeats.
Drivetrain Model A automobile When implemented in the Ford Model A automobile, the Model A engine was coupled, via a 63-pound flywheel, and clutch, with a traditional three-speed, sliding gear ("sliding-pinion" type), manual transmission (compared to the earlier Model T's planetary band-type gearbox)."Ford Model A Automobile," Smithsonian Snapshot, Smithsonian Institution, retrieved November 27, 2022
The Ford three-speed, selective sliding gear transmission (with 1-speed reverse) initially came (on early 1928 cars) with a multiple-disc clutch (as on the Model T), but it was eventually replaced with a single-plate clutch. There were no synchronizers, making "double clutching" a useful skill for Model A drivers.
The drivetrain ended at the wheels with the final drive ratio of 3.77:1. On a typical Model A, this typically provided 25–30 miles per gallon, and speeds up to 65 miles per hour.
Model AA truck When the Model A engine is implemented in the 1.5-ton Ford Model AA truck, the engine serial number – normally preceded by the single letter "A" – is, instead, preceded by "AA", denoting the implementation of a stronger clutch spring, to accommodate multiple-disc clutch units, or (for single-disc clutch units) the AA-7563 clutch pressure plate and its cover assembly, or units with the 4-speed transmission and clutch."AA Information," AA Fords-FMAATC, Ford Model AA Type Club, retrieved November 30, 2022
Various transmissions and other drivetrain options were offered. Combinations of drivetrain equipment affected the top speed which an AA could reach, while slower, lower-geared AA's could pull with greater torque.
The AA trucks were typically supplied with the 3-speed transmission of the Model A automobile, or an optional AA truck 4-speed transmission. If equipped with the 3-speed transmission, a "Dual High" factory-option underdrive for the AA was offered. The AA's rear axles were available with two different gear ratios.
Various aftermarket drivetrain options were available, including the Warford 3-speed transmission.
Operational history and adaptations
The Ford Model A engine, produced in the millions, was one of the most mass-produced automobile engines of the 1920s and 1930s, used in automobiles, trucks, tractors, farm machinery, industrial applications, boats, military vehicles, and even aircraft.