“In fact, France had placed her hopes for the 750 kg formula on the SEFAC, a completely new car produced with a degree of national backing. Engineered by Emile Petit, author of successful Salmson racing cars, its power unit was a pair of twin-cam four cylinder engines placed side-by-side and geared together, adding up to 2,970 cc. The right-hand engine’s crankshaft drove the supercharger, while power was taken to the clutch and the offset drive line from the left-hand crank. Although the SEFAC appeared in several practice sessions it was usually a non starter. In the 1938 French Grand Prix, for which its displacement qualified it, the SEFAC did complete one race lap.”
Cited from the book “Classic Grand Prix Cars : The front-engined Formula 1 Era 1906-1960 by Karl Ludwigson p. 79
More reading (Sources):;; Schnelle Motoren seziert und frisiert / Helmut Hüten, p. 286;

SEFAC (Société d’Etude et de Fabrication d’Automobiles de Course) not to be mistaken by
SEFAC (Scuderia Enzo Ferrari Automobili Corsa) was set up by the French State as the national racing factory.
Present owner is Richard Line of Cambridgeshire. The 1948 SEFAC totally re-bodied with Emile Petit still the responsible designer, was renamed as Dommartin. This car – with the technical specifications transparently those of the old SEFAC – did not race and rests now in the Musée de Chatellerault.
According to Hans Etzrodt in the article “It had twin-ohc and semi-desmodromic valve gear.” This was also said of the Salmson GP voiturette (source, probably adapted from Chris Draper’s book “The Salmson Story”. According to me [Desmodromie p. 52] it is a full group 4 desmo-system, despite of the double coil springs. More to investigate (= added to mysteries). “Secrecy was the order of the day at Montlhéry – photographers and journalists were discouraged.”
Source of the French article parts below: “La S.E.F.A.C.” par Serge Pozzoli In: L’Album du fanatique de l’automobile; no. 29 (Oct. 1970). Translated (desmopart only):The valve-control was called “semi-desmodromic” because every (opening) cam was double (on each side) accompanied with two other (closing) cams with the function of lifting the moving cam-follower parts. Leaving the spring nothing else to do but closing the valve.

Dommartin (F) 1949-1950. Compagnie des Moteurs Dommartin, Dommartin, Somme.
The Dommartin Company was formed to exploit and race the redesigned S.E.F.A.C. racing car. This plan failed. Source: G.N. Georgano : “The complete Encyclopedia of Motorcars” p. 257.

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Pics used by kind permission from Richard Line.
[Classification = Group 4]