was the early standard; as customers demanded additional oomph, manufacturers went to six, eight, or more. The more cylinders there are, however, the longer the crankshaft has to be, making it prone to vibration and twisting problems. But by lining up the cylinders in a V, four on each side, you can attach two of them to a single place on the shaft, which will need to be only about half as long.

The American V-8 engine appeared in 1907 and was made standard on Cadillacs in 1914, but it remained a luxury item until the 1932 Ford V-8, Henry Ford’s last great triumph. By casting the engine in a single block, Ford made big-car power cheap enough for anyone who could afford a new vehicle in the Depression (or steal one; the V-8 elicited fan mail from the outlaws John Dillinger and Clyde Barrow). Two-plus decades later the 1955 Chevrolet Bel Air introduced the “small block,” a light, inexpensive overhead-valve V-8 that started the “muscle car” phenomenon. Its’ descendants still form the basis for today’s Chevys.

The visceral thrill of stepping on the gas and feeling the engine’s smooth, quiet surge of power lies at the heart of our century-long affair with the automobile. The V-8 engine fulfilled America’s democratic ideal by making that thrill available to everyone.

Four-wheel hydraulic brakes (1920)

Early automakers concentrated on making cars go, not making them stop. Braking, after all, is simple; you just press something against the wheel rim. But mechanical brakes, with their wires and cables, broke down often and wore unevenly, making them pull to one side. Stopping a car took a strong forearm and lots of room.

In 1918 the airplane builder Malcolm Loughead (later changed to Lockheed) patented a braking system in which fluid transmitted pressure from the driver’s foot to all four wheels. The result was quicker, smoother stopping with no pull and fewer trips to the shop. Loughead’s system first appeared in the 1922 Duesenberg. In 1924 the Chrysler Six became the first production car to use it. Ford, as usual, was last to make the change, in 1939.

Four-wheel hydraulic brakes made driving safer, and by reducing the physical effort required, they allowed Detroit’s leaden behemoths of the 1950s and 1960s to be driven by sixteen-year-old girls. Moreover, efficient and reliable stopping lets Americans complain seriously that a speed limit of seventy-five miles per hour is too constricting. The eternal American obsession with speed has thus been able to continue its seamless progression from horses to steamboats to railroads to automobiles.

Balloon tires (1923)

Horse-drawn carriages did not have much padding, but fortunately old Dobbin couldn’t pull hard enough to give riders too big a jolt. When cars started scorching at twenty miles per hour over rutted country lanes, though, the shaking was intolerable. Improvements came on many fronts: paving materials, shock absorbers, independent suspension. The biggest change occurred where

the rubber meets the road.

Bicycle-style pneumatic tires did a fair job of cushioning early autos but were increasingly inadequate as the vehicles got faster and heavier. They were only about four inches wide and required around sixty pounds of pressure, which did not provide much give. As the car industry grew, tire makers developed new recipes for rubber and learned to incorporate belts of cord fabric. In 1923 Harvey S. Firestone used these advances in his balloon tire, which was six inches wide and required only about thirty pounds of pressure. It was an instant hit. Just as important as the smooth ride and easier steering, low-pressure balloon tires blew out much less often. Spares were banished from the fender or running board to the trunk, and the days when fixing flats was a routine part of an auto excursion were gone forever.

Duco lacquer (1923)

“Any customer can have a car painted any color he wants so long as it is black.” Unlike most pithy quotes attributed to famous men, Henry Ford actually said this, and his reason, as usual, was based on speeding up production: Black lacquer dried the fastest. That was important, because as car sales exploded during the 1910s and 1920s, painting became an ever-bigger bottleneck. The moving assembly line could build a car in a few hours, but applying varnish and waiting for it to dry took at least a week, and often much longer. One manufacturer observed that without a solution, “it would have been necessary to put a roof over the entire state of Michigan to get storage space great enough.”

In the early 1920s Du Pont chemists devised a paint based on pyroxylin (similar to guncotton, an explosive with which the company had much experience). It dried fast —too fast in early tests, when a spray would turn to powder before hitting the car. In late 1923 General Motors introduced Duco lacquer on its Oakland line, and the pale “True Blue” finish was an instant hit. Suddenly painting times were measured in hours instead of weeks, and the last vestige of craftsmanship had been banished from large-scale domestic car manufacture. By 1935 heat lamps had made drying a five-minute step.

Unibody construction (1933)

Early cars were built like the carriages they replaced, with a wood-and-sheet-metal body, usually open to the elements, bolted onto a sturdy chassis. After World War I, auto design threw off the yoke of tradition, and by the late 1920s most cars had enclosed bodies made completely of steel except for the roof. The improvements in welding and metallurgy that had made all-steel construction possible suggested a further step: merging the chassis and body into a single unit. The 1934 Chrysler Airflow had such a unitary body; it was so strong that as a promotional stunt one was pushed over a 110-foot cliff and then driven away under its own power. But the Airflow’s many other innovations made it

too revolutionary for Depression car buyers. It was the industry’s most notorious flop until the Edsel.

The 1940 Nash 600 series revived the concept, but war soon intervened. For many years after, the unibody’s advantages—lightness, ruggedness, safety, more interior room —were considered less important than the styling possibilities the old system allowed. Besides, American makers were reluctant to scrap their entire system of designing and building cars. Not until the oil crisis of the 1970s did unibody construction become generally accepted, its adoption allowing the American car industry to escape its postwar decline and start building nimble, reliable vehicles that could compete with the growing flood of imports.

Automatic transmission (1939)

Automobile engines run best at several thousand revolutions per minute, which must be geared down to drive the wheels. Changing speeds and road conditions call for different gear ratios, so shifting is required. In early cars this was done by sliding the appropriate gears in and out of place. The procedure was far from easy, especially the dreaded double declutching; if you didn’t do it right, your gears would be stripped. The Model T had a planetary transmission that was much simpler, but it could accommodate just two forward gears.

The 1929 Cadillac introduced Synchromesh, in which all gears are kept constantly in place, the unused ones turning freely on the shaft. Shifting was much easier and less perilous, but it still required simultaneous manipulation of the accelerator, the clutch, and the shift lever. To eliminate this nuisance, car makers began offering semiautomatic transmissions in the mid-1930s. The first fully automatic fluid-operated design appeared as Hydra-Matic in the 1940 Oldsmobile; today’s torque-converter design made its debut as Dynaflow in the 1948 Buick Roadmaster.

The automatic transmission removed the driver’s last tangible connection with the rough-and-tumble under the hood and made motoring more like using a toaster than operating a lathe. With the act of driving less inherently macho, power replaced elegance in car design as postwar youths and breadwinners resorted to chrome and fins to assert their masculinity. At the same time, the automatic transmission was the first major item in a car that most mechanics couldn’t fix and most drivers couldn’t even explain. Its introduction marked a symbolic distancing between Americans and their technology — from the clever application of familiar principles to an era where the machines that make up our everyday lives might as well run by magic.

Air conditioning (1950s)

The actor George Clooney of television’s “ER,” reflecting on his busy life, recently told Entertainment Weekly : “Driving for me is therapy. That’s my one place where I won’t be hassled.” Quite a change from early in the century, when drivers had to contend with terrible roads, constant mechanical malfunctions, and the vagaries of weather. Many advances have led to the car-as-pleasure-palace mentality, from enclosed bodies in the 1920s to stereos, telephones, and faxes today. But the most important

is automotive air conditioning. Would Clooney find driving so soothing in hundred-degree heat?

Though inefficient water-based systems go back as far as 1902, Packard introduced modern automotive air conditioning in 1939, to little public interest. It was revived as a luxury after-market item in Texas—where else? —in the early 1950s. Ford and GM first offered factory a/c in 1953, and since then it has become nearly universal, despite its high cost and power consumption. The result: Commuters can now spend hours crawling through traffic in Phoenix or Las Vegas without roasting to death. Automobiles created the suburbs, but it took automotive air conditioning to create suburban sprawl and make the Sunbelt just as overcrowded as our old-fashioned cities.

Catalytic converter (1975)

In 1896 Pedro G. Salom of Philadelphia, an electric-car enthusiast, scoffed at the future of internal combustion: “Imagine thousands of such vehicles on the streets, each offering up its own column of smell!” Americans learned to put up with it, just as they had put up with a different sort of pollution from horses. As decades went by, though, the problems associated with automobile exhaust — medical and environmental as well as aesthetic—became too great to ignore.

The Clean Air Act of 1970 mandated huge reductions in the worst pollutants. Car makers responded with the catalytic converter, introduced on 1975 models, which uses finely divided platinum and palladium to turn nasty carbon monoxide into relatively benign carbon dioxide. By 1981 the catalytic converter, in combination with unleaded gasoline and redesigned engines, had cut most major pollutants by 70 percent. A trip to any freeway will reveal that the smog problem still remains, but the catalytic converter has bought several decades of time for America’s car culture until new solutions—perhaps using Salom’s beloved electric propulsion—can be developed.

Microprocessors (late 1970s)

Most of the items on this list had a big impact in one particular area of driving. The influence of microprocessors has been less dramatic but much more pervasive. With computerized suspension and ignition systems, fuel injection, anti-lock brakes, pollution control, and many others, some modern cars contain more than a hundred separate microprocessors, each doing its part to save lives, fuel, and annoyance.

The microprocessor was invented in 1970, and one early manufacturer was Motorola. As its name implies, the company had long-standing ties to the automotive industry; forty years earlier it had built the first car radio. In 1975 Motorola designed a simple chip for General Motors that recorded distance traveled on a trip. Two years later Ford asked Motorola for an electronic device to control fuel flow, spark timing, and combustion in its 1980 models. Today almost every aspect of a car’s performance can be governed by microprocessors, down to planning a route and adjusting the position of the driver’s seat. While some of these advances have been of questionable value—like talking dashboards or computer-simulated dials instead of real ones —the main

value of microprocessors is the way they allow engineers to make adjustments, or even virtually redesign components, by simply putting in a new chip. This flexibility eases the conflict between innovation and mass production that has caused so many problems for the American automobile industry.