[4] Early testing revealed handling problems which were solved by adding a homokinetic joint to the suspension system suggested by Bruce McLaren, one of the drivers of the Cunningham team.

There were also ventilation problems and excessive rear tyre wear which were never resolved because of lack of proper testing due to the cars being completed shortly before the LeMans race.

The 151 driven by Hansgen and McLaren lasted the longest and was at the fifth place in early morning but experienced a transmission failure and retired after 178 laps.

Improvements included a 4,941 cc (4.9 L) engine derived from the 5000 GT but with single ignition and Lucas indirect injection rated at 430 hp (321 kW).

[6] For 1964, the changes included a new 37 inch tall body designed by Piero Drogo (built by Allegretti), a lengthened chassis, a wider track and a switch to dry sump lubrication for the engine, reducing the power output to 410 hp (306 kW).

[7] It performed well during the race recording a top speed of 310.0 km/h (192.6 mph) on the Mulsanne Straight but retired after 99 laps due to electrical and braking issues.

Other modifications included the re-adoption of dual ignition, increased fuel capacity of 160-litres, a modified front suspension, a redesigned tail and large girling disc brakes.

Tragedy struck when driver "Lucky" Casner was killed in an accident during the official testing weekend for the 24 Hours of Le Mans in May of 1965.