Compared to the fact, that the Giulietta Sprint Veloce was a dominating factor in GT-1.3 racing already from 1956, there weren't many of the cars entered in the 24 Heures du Mans in period. Just as today, Le Mans was the most demanding race on the calendar, and it almost certainly required works assistance to prepare and enter a car. Alfa Romeo had taken part in the 1953 world sports car championship with a fabulous driver line-up and a powerful car; the six-cylinder 3.5 liter 6c3000CM. Three cars were entered at Le Mans with Fangio, Kling and Sanesi as captains; they all retired, and Alfa Romeo simply didn't return to Le Mans before 1965.
In the meantime lots of Giuliettas were raced all over Europe by private entrants, but - as mentioned above - the SV didn't find its way to the start line-up at Le Mans. In 1959 Virgilio Conrero did enter two SV cars for Rosinski/Bobrowski, but they did not start the race - almost, but no cigar!
Actually, Virgilio Conrero does have an important role in getting Giulietta Sprint Veloce Zagatos to Le Mans: Max Hoffman, the north american importer of Alfa Romeo, had introduced a high-powered version of the Giulietta Spider for 1957. Conrero did the final assembly of these first 100 cars, and the only car from this batch to stay behind in Europe was entered for Le Mans that year by owner Alfranco Pagani, who had driven it in the Mille Miglia as well. At Le Mans, he had to enter it in the Sports-1.5 class, because there was no 1300 class, but when june came, he didn't even turn up for scrutineering.
Giuliettas first competed in the 24 Hours of Le Mans in 1958, four years after it was first introduced. The entrants were two Sprint Veloce Zagatos prepared by Conrero. One driven by Ubezzi/Catulli (#36) and the other by Hébert/Lauga (#37). As in subsequent years, the great french classic turned out to be an unfortunate affair, as both Alfas were forced to retire: Jean Hébert got the worst of it. On lap 59 he had an accident at the end of the Mulsanne straight, where his car burst into flames and was destroyed, but the driver got away with only slight injury. The other car was already out by lap 31 after having fuel feed problems. The Porsche 718 RS ran away with class victory in the S-1.5 class, and although Virgilio Conrero entered two cars again for 1959, this time "standard-bodied" Sprint Veloce cars, they did not start the race as mentioned to begin with. This year there was a proper GT-1.3 class, and it was won by debutante Lotus with the new and advanced Elite.
1960 and 1961 mimicked the efforts from 1958/1959, in so far that only two cars were entered; both prepared by Virgilio Conrero, followed by a DNS (did not start) entry the following year. For 1960, when Frère/Gendebien won in the high-screen Ferrari 250 TR, the A.C.O. used a test-weekend for the first time, and it is listed that Conrero entered a "Giulietta Veloce", but did not turn up. I can't find accurate evidence anywhere, but it seems possible that a special 1150cc engine was prepared by Conrero for Bernard Consten and Francesco di Leonibus; especially because Consten was a very famous local french rally driver, with many wins in Giuliettas. The small-engined Giulietta Special retired on lap 96 with gearbox failure after the GT-1.3 Giulietta SVZ was out already by lap 66 with transmission fault. As mentioned, 1961 only saw the, by now expected, entry of an "Alfa Romeo" from Squadra Virgilio Conrero" - but a no-show at scrutineering.
For 1962 something changed, and Conrero simply stayed away. He was replaced by Scuderia Sant'Ambroeus, a rewamp of the original Scuderia Ambrosiana that was started by Lurani, Viloresi and Cortese as a Milano-based race team in 1950. This time the italians showed up properly for the test weekend with two well-prepared Giulietta SZ Coda Tronca racers for two identified drivers, Giancarlo Sala and Giancarlo Rigamonti. The Coda Tronca (also known as the SZ-2) had been revealed late 1961, and was only just ready for competition in june 1962. The race became the best outing for the Alfa Romeo Giulietta at Le Mans, when Sala/de Luca came home at a P10 overall, following Hobbs/Gardner in a Lotus Elite. The Alfa, despite weighing 190 kg less than the Lotus at 630 kg, having completed 277 laps against the british car's 283 laps. The other Sant'Ambroeus entry of Foitek/Ricci retired after 225 laps with a blown clutch.
The last year with Giulietta participation would be 1963, where Scuderia Sant'Ambroeus also fielded two cars prepared by the Facetti workshop. Carlo Facetti had taken over from Virgilio Conrero as master-tuner of Alfa Romeo engines, and he had also prepared the two cars of the previous year. For 1963 the cars had the 1.6 liter engines that came with the Giulia T.I. Super that year. The light weight boxy saloon had been presented at Monza in spring and the engine was also fitted to the Sprint Speciale. Facetti did a good job and fitted engines to two cars for Sala/Rossi and Biscaldi/Kim, while team manager Eugenio Dragoni prepared the team with usual focus on quality and endurance. There was another car; a similar Giulietta SZ-2 entered by the Swiss Scuderia Filipinetti. That car placed as best qualifier in the GT-1.6 class, and something indicates that the engine was at a higher state of tune than the Facetti cars of Dragoni's equipe, because despite Q1 the Filipinetti car was retired with broken valve-gear already after seven laps.
Special work had been carried out on the Sala/Rossi car, including a ground-up fairing that made it particularly fast. As always, the Alfa Romeo's adversaries were the Lotus Elites which, despite SZ fine tuning, still had more than four seconds a lap on the Italians. At first the british cars got off on the wrong foot; Pat Ferguson put his Lotus in the Mulsanne sand trap on lap one. By the end of the first hour, the Elite of Gardner/Coundley was leading the class, only to be soon pushed out by the SZ cars, initially by Biscaldi/Kim in the second hour and then by Sala/Rossi - and there they stayed until 6 o'clock the following morning. A little later, the differential suddently went as Romolo Rossi charged into the Maison Blanche corner - the special fairing had made the diff overheat. The other Sant'Ambroeus car had already been disqualified for taking oil on earlier than it should have done, so the class was won by the Wagstaff/Ferguson Elite, which had been able to pull itself out of the sand to begin a gradual recovery.
The Giulietta Tubolare project had started in 1962, and a functional prototype had been finished. But the final shape, developed by Zagato as an evolution of the Giulietta SZ Coda Tronca, was based on tipo 105 running gear and the new 1.6 engine from the Giulia SS. Giuseppe Busso had overlooked the project from Portello and the car was ready for the 1964 Le Mans - entered by Scuderia Sant'Ambroeus. Although the concept was developed as a Giulietta Tubolare, it in reality became a Giulia Tubolare Zagato, and after Alfa Romeo founded the Autodelta works with Carlo Chiti at the helm, the car quickly evolved into a best-in-class; first with double-ignition GTA engines and for 1965 as the TZ-2, with a much lower body in fibreglass and with a dry-sumped GTA engine - but the same tubular chassis.
In the 1964 edition of Le Mans Sant'Ambroeus placed P13 and P15 overall (and with a third car retiring on lap 47 following an accident). In 1965 Chiti's Autodelta team came with three TZ-2 racers; the Zeccoli/Rosinski car (#43) crashed on the first lap, the Gekko/Zucolli (#42) car stopped on lap 22 with a burst oil pipe in the dry sump oil curcuit and Businello/Rolland car (#41) almost lasted to the end before it was retired on lap 217 with crashed bearings. Two private entrants had the older TZ-1 cars: From Luxemburg, Koob/Finkel in the Eqiupe Grand Ducale car (#44) that expired on lap 218 with engine fault and another private TZ-1, that was entered by Alain Finkelstein, but it didn't show up for scrutineering.
From 1967 Autodelta started a long run of Tipo-33s, with best results in 1968, when they actually fought for outright victory, but 1966 was in fact the last of the old days for Alfa Romeo: Autodelta entered four Giulia TZ-2 cars, and Ecurie Francorchamps entered two TZ-1 cars. But, alas, none of them showed for the race.
Chiti and his boys were preparing for a proper comeback in a car they really-really loved: The Tipo 33. A whole other kind of car than the Giulietta.