In 1912 three racing drivers and a forward thinking draftsman (early hot rodders) convinced Robert Peugeot to adopt a radical new approach to Grand Prix racing engine design. Conspiring with draftsman Ernest Henry they conceived the world's first dual overhead cam, four valve per cylinder racing engine, the Peugeot L76.
Grasping the core concept of optimizing engine airflow early on, they believed that feeding the engine with twin cams and more valves could realize significant power gains from a lighter and more compact engine. Peugeot was already a successful automobile manufacturer with an impressive staff of technical engineers who remained unimpressed (read that jealous) by their theories; quickly dubbing them "Les Charlatans." Along with Henry, the group included noted European Grand Prix drivers Georges Boillot, Jules Goux and Paolo Zuccarelli.
A shrewd observer of motor racing's technical challenges, Peugeot liked their bold approach and backed their effort in a small unassuming workshop in Paris. The gamble paid off handsomely. A diminutive yet powerful new 7.6L DOHC, 4-valve Peugeot racing engine emerged seemingly out of nowhere to soundly whip a contemporary 15L Fiat in the French Grand Prix, opening the flood gates to a modern era of high performance engine design not previously envisioned by the stodgy Peugeot engineering staff. "Les Charlatans" had seized the day.
Delighted and encouraged by this initial success Peugeot embarked upon a refinement program to modernize the racing powerplant to the fullest extent. In 1913 Peugeot presented a refined 5.6L version of the L76 to challenge the Grand Prix racing establishment and the Indianapolis 500. Jules Goux won the 1913 Indy 500 with the Peugeot, further cementing the Peugeot's capabilities and the soon to become legendary DOHC 4-valve engine configuration. The designers refined the engine layout, switching from shaft driven camshafts with beveled gears to a multi-gear drive arrangement for more accurate timing.
In 1914 Arthur Duray shocked the establishment by entering an independent 3.0L Peugeot in the Indianapolis 500 to compete against other 5.6L Peugeot cars and the powerful 1913 Delages sporting over 105 horsepower from their unique horizontal-valve engines. Sportswriters immediately declared the car a "Baby" racing car, but had to eat their words when the little 3L racer smashed the Indy lap record with a stunning 99.85 mph blast that had the pits all astir.
Rene Thomas in a French Delage ultimately won the race, but closely paced by Duray in the 3.0L Peugeot. The winning Delage was powered by an engine more than double the size of the diminutive Peugeot and racers quickly noted that the Peugeot engine was only 6 cubic inches larger than a current Model T Ford engine. The modern racing engine was born and began its triumphant march through history as designers everywhere copied the Peugeot DOHC, 4-valve design. In 1916 a Peugeot with the L45 engine won the Indianapolis 500 with racing driver Dario Resta at the wheel.
The key concept to this timeless racing masterpiece is the airflow enhancing inclined 4-valve top end operating in a pent-roof combustion chamber and actuated by dual overhead camshafts. One hundred years and millions of racing miles later this configuration is still recognized as one of the best designs for racing engines; a racing legacy that surpasses even legendary engines such as the small block Chevy and the Chrysler Hemi.
Multiple iterations of the DOHC 4-valve Peugeot engine were developed over a relatively short period. They included different bore and stroke combinations, valve sizes and valve actuating mechanisms. The accompanying illustration courtesy of Kenneth Walton's "Offy, America's Greatest Racing Engine" depicts two different 1913 versions of the engine based on the same lower casing. According to Walton, the left version with direct acting camshaft was used in the United States while the right hand version with additional cam follower stayed in Europe.
This right hand version led some to believe that the Peugeot's valve action was Desmodromic (fully mechanical actuation, no valve springs) when in fact both versions are spring actuated. The cam follower in the European version works in conjunction with a small helper spring in a separate housing that is part of the cam cover. Note also that the U. S. version incorporated three ring pistons while the European engine used only two rings. These designs are typical of the 3.0L engines. The 7.6L 1912 version was similar,and the later 1914 (3rd generation) version as raced by Bob Burman also had the head cast integral to the block and incorporated a 360 degree barrel type crankcase. The 3rd generation engine is the type that Harry Miller rebuilt and modified for Burman and became the basis for the subsequent Miller designs.
Valley Head Service in Northridge, California has performed specialized engine restoration for numerous owners of these rare survivors of a glorious age of motor racing. Hence it was a logical choice for the owners to commission them to restore the engine to its former splendor. The following photos are a little soft, but they still convey the ingenuity and forward thinking of "Les Charlatans" more than a century ago. Check out some of the features we still think are trick stuff even today.