Ugo Sivocci was born in Salerno, Italy. He first competed on bicycles as did his younger brother, Alfredo Sivocci. After the war he joined CMN motor-works (Costiuzioni Meccaniche Nazionali) in Milan. Enzo Ferrari had been hired by the Giovannoni garage that used to strip down second-hand light trucks and send them to Milan to be fitted with lightweight torpedo or roadster bodies. One of Ferrari’s duties was to deliver the chassis to Milan, where he became friends with Ugo Sivocci. When Enzo was in Milan, they used to meet at the Vittorio Emanuele bar and Sivocci helped him get a job installing Isotta Fraschini engines into other chassis.
In 1919 both Sivocci and Ferrari went to work for the SA Costruzioni Meccaniche Nazionali in Via Fatebenefratelli in Milan, makers of the CMN automobile. But CMN couldn't satisfy their sporting passion as they didn't make racing cars. So in 1920 Ferrari joined Alfa Romeo, followed shortly by Sivocci.
Sivocci spent his entire racing career with Alfa alongside Ascari, Campari and Ferrari. In 1920 Campari won at Mugello. He won again in 1921, when he was followed home by teammates Enzo Ferrari (2nd) and Sivocci (3rd). In 1920 Campari competes in the kilometre speed trial at Gallarate with a Grand Prix car designed by Merosi in 1914.
1921 marked the competition debut for the 20-30 HP ES Sport Alfa. Ascari and Sivocci finished first and second in the 4.5-liter class in the Poggio Berceto race in Parma.
In 1923 Alfa Romeo notched up victory after victory, with Masetti winning at Mugello. Using cars derived from the RL, Alfa took part in the Targa Florio, entering Masetti, Campari, Ascari, Sivocci and Ferrari.
Sivocci, who was a superstitious man had the famous green cloverleaf inside a triangle on a white background painted on his car. The race was over 4 laps of the Circuito delle Madonie, for a total of 432 km. Ugo Sivocci won at the wheel of an Alfa Romeo RLTF with a 3 litre six cylinder engine. Despite Italian tradition associated with the number 13, Sivocci won the race sporting that number on his radiator grille.
Ascari had dominated the race but his engine quit on the last corner and though he managed to restart the engine again, it took him 10 minutes, by which time Sivocci had taken the chequered flag. Sivocci won in 7 hours, 18 minutes driving at an average speed of 59.177 km/h.. Ascari, who posted the fastest lap time in 1 hour, 41 minutes and 10 seconds at an average speed of 63.986 km/h. came second, three minutes behind. Two other Alfa RLTF models took part in the 1923 Targa Florio, driven by Enzo Ferrari and Giulio Masetti, who finished 4th.
Ascari won again at Cremona, Sivocci came first in a Touring race at Monza, but he was later to die on the same track as the result of an accident in qualifying for the “P1” Grand Prix car in September.
Sivocci became Merosi’s chief test driver for the P1 but during testing for the Italian Grand Prix at Monza, Sivocci was killed when his car went off the road at what is now the Ascari bend. He wanted to paint the cloverleaf on the P.1's radiator, but there wasn't time, though it was going to be painted on the car before the race. The Alfa Romeo P1 was withdrawn. The car had number 17 on it. A number that is unlucky in Italy. After this accident, 17 was banned from Italian cars. There is a slight irony in the fact that his greatest victory came in a car bearing the number 13, a number that is unlucky in most countries.
Odd numbers were only used in practice at Monza, in races all cars carried even numbers. This conveniently left out 13 and 17. When in 1967, Jackie Stewart drove car No. 31, it was the first time in the history of the Italian GP at Monza that a car had carried an odd number and for years after 1967, odd numbers were still never found.