Part III of this series will cover the second version of the 16 valve Roof cylinder head along with the Roof 8 valve head. The first of the Frontenac cylinder heads manufactured by Louis Chevrolet will also be discussed.
Robert M. Roof introduced the Type “B” 16 valve, a general purpose head with 1.25 inch valves in the Fall of 1917. He changed the layout of the intake ports from his first design and ended the air leakage problems. The new rocker arm design shown here ended the rocker breakage issues suffered with the earlier unit. When used with the Ford camshaft and a standard compression ratio it produced 32 horsepower, 12 more than stock. With a Laurel racing camshaft and higher compression it produced 37 horsepower. Due to a reduction of the compression ratio at the time, the original Ford engine was rated at only about 18.
The earlier Type “A” continued on as the racing head until the Type “BB” with larger 1.5-inch valves was introduced in August of 1921. It produced between 36 and 42 horse power, depending on the camshaft and compression ratio used.
- Type “B” cutaway drawing – Production in the Roof shop – Full details of the Type “BB” racing head with larger intake ports and 1.5-inch diameter valves.
Demand for for the new cylinder heads rose in the post World War I years when racing became very popular and the advent of manufactured racing components made it easier for the average man to enter the racing game. Many county fairground oval tracks across the country soon had regular racing events in which Ford based cars often dominated. These light weight and fast accelerating cars had an advantage over many of the larger racers of the era on the short half and one mile tracks.
Laurel Motors, who manufactured and distributed the Roof line of cylinder heads, soon added racing style bodies and their own under-slinging brackets to their offerings. To feed the ever increasing demand for speed, aluminum pistons, rear end gears of different ratios, carburetors, ignition systems, crankshaft counter balances, camshafts and wire wheels from other suppliers were also made available in their catalog .
The “Roof 8” was introduced in 1922 for $75 as a lower cost alternative to the 16 valve units. It was offered the standard compression ratio with 1.625 inch valves. The higher compression racing model featured 1.687 inch valves. The standard model produced 26 horsepower while the racing version provided up to 31.
Louis Chevrolet was born in 1878 in La Chaux-de-Fonds, Switzerland. He was the second son of Joseph Chevrolet, a watch and clockmaker. His father taught him basic mechanical skills and stressed the importance of precision in the manufacture of machine parts which later contributed to his skill as an engine designer.
As was the case with many other early auto racers, Chevrolet was first involved with bicycle racing and repair. For a time he was in the bicycle manufacturing business but soon became fascinated with then new automobile after seeing an early example. He next apprenticed at the Darracq, Hotchkiss, and Dion Bouton auto factories and in 1898 he went to work at the Mors Auto Company. They sent him to an auto agency in Montreal, Canada in 1899, where Chevrolet first worked as a chauffeur-mechanic for six months and then went to Brooklyn, New York, where he worked with the DeDion Bouton Motorette Company. In 1905 he received an opportunity to become a substitute race car driver for Fiat in New York City.
His racing success soon attracted the attention of none other than William Durant, founder of General Motors who invited Chevrolet and his younger brother Arthur to Flint, Michigan, in 1907 to try out for a job as his chauffeur. A staged race behind the Buick plant in Flint was a qualifying test for the job and Arthur got the chauffeur’s job because he was a more careful driver. Durant put Louis Chevrolet, who easily won the race right to work on the Buick racing team. For the next three years, Louis a hard charger scored many victories for the team.
In 1909, he went to Detroit where he began to design, build and test four and six cylinder automobile engines. When Durant was forced out of General Motors in 1910 because of a stockholder’s dispute, Chevrolet designed a small and luxurious touring car for him. The resulting car was a six-cylinder model (named the Chevrolet). In 1914, when Durant added a cheaper car to the line in order to compete with Ford, he sold his stock in the Chevrolet automobile to Durant, as he did not want his name to be associated with low-priced cars and he had also wanted to return to racing arena.
Chevrolet then designed of his own line of racing cars and founded the Frontenac Motor Company in 1914. The pre-war cars were very sucessful and the post-war models won the Indianapolis races in both 1920 and 1921. Working with engineer C. W. Van Ranst the two also designed a very modern and advanced Frontenac road car with outside investors. Unfortunately as with many others it was a victim of the post World War I econonic recession.
Soon after this Chevrolet and C. W. Van Ranst then designed the first in a series of special overhead valve cylinder heads for the Model “T” Ford late in 1920 and early 1921. Named Frontenac, the heads were available in three versions; The “T” aimed at trucks and touring cars, the “S” for speedster use with a higher compression ratio and the all out “R” was a racing head. These heads were well built, and soon became popular on the 1/2 and one mile racing tracks across the land. When we return to this series, we will cover more about this head, the next model, the S-R racing head, and the DOHC 16-valve will be covered. You can look back on Part II of this series here.