Carlo Castelbarco appears only to have raced for one season, 1933. It started with finishing second overall in the Mille Migilia and ended with involvement in the fatal accident of Borzacchini and Campari at Monza in September.
Carlo Castelbarco appears only to have raced for one season partnering Cortese in the Mille Miglia that year. Castlebarco had bought a brand new eight cylinder Alfa Romeo Monza however on the eve of the race the car caught fire as it was being readied. Cortese found the car just four hours before the start with the fuel tank, tail and tires, along with the electircs, a mass of molten metal. By canibalising another car and with all hands to the pumps the car was back together with an hour to spare. Then a mechanic put water in the fuel tank and the car had to be returned to the workshop for further work. Eventually they took the start only a few minutes late, having driven across Bresia at an alarming rate. Cortese did all the driving and their work was rewarded by finishing 2nd overall in the now decidedly second hand looking Alfa.
At the end of April he came 3rd in heat one of the Circuito Pietro Bordino in Alessandria and 8th in the final in his Alfa Romeo.
At Parma-Poggio di Berceto Carlo was 5th overall in the 2300 Monza whilst Luigi was 11th overall in his 1500 Maserati. So Carlo and Luigi did race against each other at least once.
At Colli Torinesi hillclimb (11/6/1933) Carlo was 1st overall and 1st in the "Corridori dilettanti" category.
At the Pontedecimo-Giovi climb Carlo (18/6/1933) was 8th overall, 1st in the oltre 1500 cmc sport class.
In Sardinia Carlo was 2nd overall and 2nd in his class in the C.Sassari (29/6/1933)
A 3rd overall (1st in class) was achieved at Varese-Campo dei Fiori (9/7/1933) plus fastest "dilettanti".
The Principe di Piemonte at Avellina (6/8/1933) for sports cars proved a great disappointment as Carlo was in 4th place overall when he ran out of fuel just a kilometre from the finishing line. At one stage in the race he had been in second place.
Another retirement followed at Pescara when he had mechanical trouble in the Targa Abruzzo (13/8/1933) early on.
The Italian Grand Prix, which was initially scheduled for July 25, was postponed until September 10 due to upgrading work at Monza. The Grand Prix of Monza was already scheduled for the same day which meant that two major races were held on the same day at the same circuit.
In the morning Carlo was 6th in the Italian Grand Prix. Then, in the second heat in the afternoon for the Monza Grand Prix, tragedy struck.
The start had been delayed due to oil on the track in the South Curve from the morning's racing and the assembled drivers had been notified and warned of the situation. When the flag dropped, Borzacchini and Campari immediately took the lead closely followed by Carlo Castelbarco and Barbieri. As they came into the South Curve for the first time at around 180 kph, Campari moved to the right to avaoid the oil. Unfortunatley he lost it in the damp conditions and after sliding along the concrete retaining wall, his car went over the side, flipping end over end down the embankment. Campari was killed instantly, crushed under his car. Borzacchini, who was attempting to overtake Campari, also lost control, flew over the retaining wall and was thrown out against a tree. He was rushed to hospital in Monza with multiple internal injuries and a fractured spine. He died soon after being admitted.
Castelbarco who had overtaken Barbieri, skidded and overturned on the outside and though his car landed on top of him and he escaped with only minor cuts and scratches. Thus, brutally exposed to the dangers of racing in those days, he retired forthwith, after a brief but promising dabble in motor-racing.