Tech Analysis

In the mid-1980s, automotive engineers "discovered" multi-valve engines. A regulatory push for lower exhaust emissions and higher fuel economy, coupled with customer demand for cars that could and would perform as well as cars from a generation earlier, led car companies to designs of powerful and efficient four-cylinder engines. A horsepower race of sorts had developed, and small-displacement engines could produce big numbers if they ran at high engine speeds.

Four Are Better Than TwoTo help these small engines breathe at high speed required large intake and exhaust valves. But the combustion chamber size limits the size of the valves, and it was found that two small intake and two exhaust valves would breathe more efficiently than a single large intake and large exhaust valve. This was especially true in the short-stroke high-speed engines that were popular in Europe and were starting to show up in America.

However, the angle with which the intake and exhaust valves enter the combustion chamber also affects gas flow, and activating the valves with a single camshaft was difficult if the optimum valve angle were to be maintained. Enter the twin overhead camshaft engine. Actually, twin-cam engines entered a lot sooner than the mid-1980s. In fact, right from its inception in the early 1900s, the twin cam has remained the engine to beat on racetracks from Indianapolis to Le Mans.

In The BeginningGottlieb Daimler created the first automotive internal combustion engine in 1885. In 1891 Peugeot produced its first automobile, a Daimler-engined quadricycle, and in 1894 finished second and third in the world's first organized auto race, held between Paris and Rouen. By the early 1900s, Peugeots were regular competitors, usually running small-car classes with huge single-cylinder engines with great success. In 1910, Paulo Zuccarelli beat the mighty Peugeot team with a small-displacement four-cylinder Hispano-Suiza. Peugeot drivers Jules Goux and Georges Boillot knew they needed a new kind of engine and convinced Zuccarelli to join their team. Then they went to Robert Peugeot, the president of the company, with an idea. They proposed an all-new racing engine to enter the Grand Prix circuit. He liked the idea so much that he commissioned a car from the three drivers as well as another car from young Ettore Bugatti. Peugeot decreed that the faster of the two designs would win the Peugeot name and the contract.

Les CharlatansThe three racing drivers, knowing they were in over their heads, added Ernest Henry from Switzerland to their team. Henry is a bit of an enigma. Variously described as merely a draftsman or as the true genius behind the new design, little seems to be known about his formal engineering training. He had worked at one point for Picker, a marine engine company in Geneva, and no doubt picked up much of his practical knowledge there. One thing is certain, the engineering staff of Peugeot did not like the idea of a small team of drivers and outsiders designing their racing cars, labeling the group Les Charlatans.

Bugatti built a car whose best speed was 99 mph. Les Charlatans beat that by more than 15 mph, so Robert Peugeot gave his name to their car. In fact, the complex racer carried not one existing Peugeot part. What it did have was a beautifully executed 7.6-liter twin overhead camshaft 16-valve four-cylinder engine with a modern hemispherical combustion chamber. But this engine wasn't the first to use two camshafts. They had been used before, located in the cylinder block of relatively inefficient T-head engines. In 1905 Delahaye had experimented with a double overhead camshaft with six inline valves per cylinder for a marine racing engine and set a new world's speed record on water.

Les Charlatan's Peugeot, though, was the first automotive application of the twin overhead cam concept and set the pattern for all future twin-cam designs. The first race the team entered was the Grand Prix de l'ACF at Dieppe on June 26, 1912. Boillot beat the favored 14-liter Fiats by 12 minutes after two full days of tough racing. The following year, Jules Goux took the twin-cam Peugeot to Indianapolis and beat the field by 13 minutes after 500 miles.

The Great WarLes Charlatans didn't last long. Zuccarelli was killed in practice shortly before a Grand Prix in 1913. Boillot went into the French air force during the war and was killed in a dogfight with the Germans. Jules Goux also entered military service and after the war continued racing, including a few more attempts at Indianapolis in the 1920s. Ernest Henry, unhappy with his treatment by Peugeot's mainline engineers, left the company and designed twin-cam racing engines for Ballot and Sunbeam in the early 1920s. He eventually fell into obscurity and died in poverty in 1950. His Peugeot twin-cam engine, perhaps one of the most successful racing engine designs of all-time, became the model for a large number of copies from companies like Delage, Fiat and Nangent in their racing cars. It also was the starting point for Harry Miller's brilliant run of racing engines that as Offenhausers were still winning races in the mid-1970s.

A Good ConceptA number of other twin-cam racing engines appeared in the early to mid-1920s, mostly from English and French companies. In 1921, American Fred Duesenberg brought the twin-cam concept to his racing engines and won the Indy 500 in 1924, '25 and '27. In 1928 he established a twin-cam production engine for the company's superb line of high-performance luxury cars. Stutz followed in 1931 with the 32-valve eight-cylinder DV32.

Alfa Romeo built its first twin-cam engine as far back as 1914, a one-off 4 1/2-liter four-cylinder Grand Prix engine, but it never ran in international races. Alfa was to become one of the twin cam's greatest proponents through the efforts of Vittorio Jano, beginning in 1926 with the highly successful 1500cc and later 1750cc six-cylinder sports cars. In supercharged form, these cars won all the great sports car races except Le Mans from 1928-30. Le Mans fell to Alfa from 1931-34 with Jano's next design, a 2.3-liter straight eight with double overhead cams. The same engine also powered Alfa's successful Grand Prix car of the period. In 1934 Jano's six-cylinder twin-cam 2.3-liter engine became the Alfa engine of choice and remained in production into the early post-war years.

Bugatti entered the twin-cam ranks in 1931 with its Type 51 straight eight, a twin-cam development of the very successful Type 35 single overhead cam engine. The twin cam owed most of its valvetrain design to a pair of Harry Miller's racing engines that Bugatti had purchased and carefully examined in 1929.

Mercedes-Benz began experimenting with twin-cam engines in 1922 under technical director Paul Daimler. Ferdinand Porsche took over his duties when Daimler left the company at the end of 1922 and oversaw an Indianapolis effort in 1923 that resulted in eighth- and 11th-place finishes. Ultimately these early efforts led to the twin-cam engines in the all-conquering silver arrows Mercedes-Benz Grand Prix cars of the late 1930s.

The Jaguar XKWhile specialized racing engines and virtually hand-built Duesenberg and Stutz models took advantage of the better breathing afforded by double overhead camshafts, very few production cars, particularly those made in America, had anything more sophisticated than side-valve engines through the end of the 1930s and into the 1940s.

In fact, overhead valves were considered quite advanced when they appeared on Oldsmobile's Rocket V8 engine and Cadillac's V8 of 1949. That's why William Lyon's remarkable double overhead cam six-cylinder Jaguar XK engine seemed so radical when it was introduced in 1948. William Heynes, Walter Hassan and Claude Baily designed this engine-which remained in production through a number of iterations well into the 1980s-during the war. The double overhead camshafts were chain driven, greatly simplifying the gear-drive systems that were popular before the war. Its original purpose was to power a luxury sedan, the Jaguar Mark VII.

To advertise the new engine, Lyons had a sports car built around the new powerplant for the 1948 Earls Court motor show, and the XK120 was born. The car was a hit, as was the MkVII sedan of 1950 that the engine was originally created for. But the XK120 was pure glamour, and in time this engine became the definitive sports-car engine. It powered Jaguar cars to victory in the 24-hour race at Le Mans no less than five times.

OthersThe clever Jaguar engine was joined by a twin-cam six-cylinder engine in 1950 in the Aston Martin DB2. Aston Martin had experimented with twin-cam engines in the early 1920s. The new engine, originally designed by W.O. Bentley for the 1948 Lagonda, had a long and useful life in Aston sports cars and led to a Le Mans win in 1959.

The beginning of the 1950s also saw the introduction of the new 1900cc four-cylinder from Alfa Romeo. This engine marked a departure for Alfa, from it being a small maker of expensive and prestigious sports cars to a large-scale producer of mainstream automobiles. Lightweight and powerful, the 1900cc engine formed the basis of Alfa powerplants for the next three decades. The 1300cc twin cam came in 1954, followed by 1600cc, 1750cc and 2000cc versions. These were high-volume engines yet were beautifully made and delightful to listen to, whether in a sedan or sports car.

Other small but highly successful Italian sports-car manufacturers like Maserati and OSCA and Spanish builder Pegaso turned to twin-cam designs in the early through mid-1950s with great success. Ferrari joined the twin-cam ranks in 1949 when Aurelio Lampredi converted Gioacchino Colombo's single-cam V12 Formula One engine, but it wouldn't be until the 1960s that a Ferrari GT car would be available to the public with a twin-cam engine.

Following his success with the Jaguar engine, Walter Hassan joined with Harry Mundy of BRM V16 fame in 1953 to create the 2.5-liter Coventry Climax V8. Although not immediately successful, this engine led to the highly successful 1.5-liter Coventry Climax four-cylinder engine for Formula 2. Used by Lotus and a wide range of other racecar builders in England, the Coventry Climax engine was lightweight and powerful. It was popular in both sports car and formula car racing.

Aurelio Lampredi moved to Fiat from Ferrari and in 1966 introduced the 124 Sport that used twin belt-driven overhead camshafts. The Fiat 124 and its twin-cam engine came at a time when most other inexpensive sports cars like the MGB and Triumph TR4 were still using pushrod engines. The use of a rubber toothed belt by Fiat made the engine much quieter and less expensive to build than previous twin-cam designs. The Fiat twin cam remained in production well into the 1980s and was used in sports cars, coupes and sedans.

FordAlso created in the 1960s were two Ford twin-cam engines, neither of which was actually designed by Ford. The Lotus twin cam used a Cortina four-cylinder engine block topped with a special twin-cam cylinder head. Used in Lotus sports cars and Ford sporting sedans like the Lotus Cortina and Ford Escort, the engine was a great success, especially in competition. In 1967 Keith Duckworth and his Cosworth Engineering company designed another Ford-based project, the Ford Cosworth V8. Highly competitive, readily available and extremely reliable, the Ford Cosworth DFV Grand Prix engine and DFX Indycar engine opened the modern era of professional racing and remained viable for more than a decade.

New Problems To SolveBy the time the 1980s arrived with the seemingly conflicting needs for high efficiency, low emissions and good performance, the twin-cam concept had already been in use for nearly 70 years. Toyota, with the Corolla FX16, was one of the first Japanese cars that came to the U.S. with the exotic valvetrain. Soon, many cars from Japan carried the 16-valve double overhead cam four-cylinder engines that signified performance to a whole generation of enthusiasts who had never heard of a Peugeot Grand Prix car or a Coventry Climax engine. In time, refinements appeared, like the Honda Prelude with variable intake valve timing, to improve power and emissions, a concept that had been introduced first by Alfa Romeo earlier in the decade.

One Good IdeaAmerican manufacturers, once among the leaders in twin-cam technology with Duesenberg, Stutz and Miller, were slow to catch up. Pushrod overhead valve engines had become so entrenched that the introduction of a special Vega with a Cosworth twin-cam cylinder head in the 1970s was considered to be exotic in the extreme. But in the beginning of the 1990s, American manufacturers developed engines that used the technology. Even the Corvette, a long holdout for pushrod powerplants, was available for a time with a ZR-1 V8 engine whose complex twin-cam cylinder head came from Lotus Engineering and was manufactured by Mercury Marine. Today most European automakers are heavily invested in twin-cam multivalve engines. Ford, DaimlerChrysler and General Motors and Japanese companies all have twin-cam engines in production. But look at them closely, and it is easy to see that their theory, design and execution still display the original concepts Ernest Henry and Les Charlatans pioneered in that 1912 Peugeot.