than today's. The various manual control tasks (such as manual choke and spark advance) and the method of use (such as hand throttle) were typical for automobiles of the era, although they might seem more like farm tractor operation to most automobile drivers of today. 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, with the thumb tucked under the handle (not clasped over top of it), 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 the engine was started with a rapid pull of the crank handle. In good tune, an already-primed T engine only has to be cranked half a turn for it to successfully start. The T's planetary transmission is famous for its differences from what later became the norm for car transmission operation. The 3 foot pedals are not used in the way later cars use their pedals. Operation is not difficult but requires "unlearning" habits used with later vehicles. Design changes over the years The following major changes were made (listed by year): 1909 — First model year - Water pump was discontinued; subsequent Model T engines used thermosyphoning to circulate the coolant. 1911 — Valve covers were added 1917 — Higher head with larger water jacket 1919 — Engine starter introduced as an option 1920 — Lighter-weight rods and pistons 1922 — The cylinder casting was changed so a single valve cover could be used 1926 — An extra boss was added at the rear for two additional bolts stiffening the transmission, 1927 — The carburetor throttle rod was re-routed over the engine Production run The T engine was produced continuously from September 27, 1908, through August 4, 1941, exactly 12,000 days. This makes it one of the longest engines in series production, especially considering that the specifications remained mostly unchanged for this entire duration. Its production run for the U.S. consumer market for passenger cars and pickups was