The Model T had a 177-cubic-inch (2.9 L) front-mounted inline four-cylinder en bloc engine (that is, all four cylinders in one block, as common now, rather than in individual castings, as common then) producing 20 hp (15 kW) for a top speed of 40–45 mph (64–72 km/h). The Model T four-cylinder side valve engine was first in the world with a detachable head, making service like valve jobs easier. According to Ford Motor Company, the Model T had fuel economy on the order of 13–21 mpg-US (16–25 mpg-imp; 18–11 L/100 km). The engine was capable of running on petrol, kerosene, or ethanol, although the decreasing cost of petrol and the later introduction of Prohibition made ethanol an impractical fuel.

A flywheel magneto was an electrical generator that produced the high voltage necessary to produce a spark to initiate combustion. This voltage was distributed by the timer (analogous to a distributor in a modern vehicle) to one of the four trembler coils, one for each cylinder. The coil created a high voltage current, directly connected to the spark plug in the cylinder. Ignition timing was adjusted manually by using the spark advance lever mounted on the steering column which rotated the timer. A battery could be used for starting current: at hand-cranking speed, the magneto did not always produce sufficient current (a starting battery was not standard equipment until sometime in 1926, though all T’s had a bat position on the coil box switch). A certain amount of skill and experience was required to find the optimal timing for any speed and load. When electric headlights were introduced in 1915, the magneto was upgraded to supply power for the lights and horn. In keeping with the goal of ultimate reliability and simplicity, the trembler coil and magneto ignition system was retained even after the car became equipped with a generator and battery for electric starting and lighting. Most cars sold after 1919 were equipped with electric starting, which was engaged by a small round button on the floor.

Before starting a Model T with the hand crank, the spark had to be manually retarded or the engine might “kick back”. The crank handle was cupped in the palm, rather than grabbed with the thumb under the top of the handle, so that if the engine did kick back, the rapid reverse motion of the crank would throw the hand away from the handle, rather than violently twisting the wrist or breaking the thumb. Most Model T Fords had the choke operated by a wire emerging from the bottom of the radiator where it could be operated with the left hand. This was used to prime the engine while cranking the engine slowly then starting the engine with the left hand with a rapid pull of the crank handle. The car only had to be cranked half a turn for it to successfully start. This “quick start” is because of the engine’s small displacement and low compression.

The car’s 10 US gal (38 l; 8 imp gal) fuel tank was mounted to the frame beneath the front seat; one variant had the carburetor (a Holley Model G) modified to run on ethyl alcohol, to be made at home by the self-reliant farmer. Because Ford relied on gravity to feed fuel to the carburetor rather than a fuel pump, a Model T could not climb a steep hill when the fuel level was low. The immediate solution was to climb steep hills in reverse. In 1926, the fuel tank was moved forward to under the cowl on most models.

Early on, the engine blocks were to be produced by the Lakeside Foundry on St. Jean in Detroit. Ford cancelled the deal before many were produced.

The first few hundred Model Ts had a water pump, but it was eliminated early in production. Ford opted for a cheaper and more reliable thermo-syphon system. Hot water, being less dense, would rise to the top of the engine and up into the top of the radiator, descending to the bottom as it cooled, and back into the engine. This was the direction of water flow in most cars which did have water pumps, until the introduction of crossflow radiator designs. Many types of water pumps were available as aftermarket accessories.