Bizzarrini P538

[Gt1Street]

Story By QV500:

Despite the undoubted potential demonstrated by Iso's A3/C during the course of 1964 and '65, Bizzarrini had a burning desire to win Le Mans outright. This meant he needed to build something even more exotic and in late 1965, a mid-engined sports prototype was conceived. Known as P538, it consisted of alloy chassis panel sections bonded together to form a totally new unit construction spaceframe. There was also independent suspension all round via unequal length wishbones at the front and trailing arms at the rear, coil springs being combined with Bilstein shocks at each corner.

The P538's Porsche-sourced ventilated disc brakes and calipers were mounted inboard of the differential at the rear whilst long-range fuel tanks in the side sills kept as much weight as possible within the wheelbase and helped achieve near perfect front/rear distribution. Campagnolo magnesium alloy wheels of a similar style to those seen on the A3/C were used albeit with much wider rims than before. Despite the fact that only four P538's were originally constructed, Bizzarrini used two types of longitudinally mounted engines for his sports prototype, Chevy's trusty 327-inch Corvette V8 and the Lamborghini V12 he designed during the winter of 1962/’63. P538's were actually the first competition cars to use the Lamborghini engine, a four-litre V12 being installed at the request of North American customer Mike Gammino who wanted a machine of pure Bizzarrini design to compete with in the inaugural Can Am series. Displacement was 3929cc (or 240-inches) thanks to a bore and stroke of 82 x 62mm respectively, the stock 320bhp Lambo dual overhead camshaft motor being considerably enhanced. Modified cam profiles and polished ports and connecting rods were combined with a raised compression ratio and six sidedraught Weber carburettors, boosting output to 419bhp at 8300rpm.

The 5.3-litre Corvette motors were similar to those found in A3/C Corsa's and tuned by Bizzarini to full competition spec, polished ports and combustion chambers being joined by hot camshafts and a free-flow exhaust. Displacement was the familiar 5354cc thanks to a bore and stroke of 101.6 x 82.6mm respectively, four sidedraught Weber 45 DCOE carbs and a compression of 10.5:1.helping output up to 430bhp at 6200rpm. All four examples ran five-speed ZF gearboxes similar to those used in Ford's GT40 and would have been well capable of reaching speeds approaching 200mph.


Bizzarrini wrapped the spaceframe chassis with a fibreglass body of his own design, the panel fabrication being undertaken by Catarsi of Livorno who, whilst undoubted experts with glassfibre, were more familiar with boats. Nearly all the panels were bonded to the chassis in order to achieve the most rigid structure possible, the nose featuring Bizzarini's distinctive nostril treatment between perspex covered headlights. A primitive plastic windscreen gave drivers little protection from the elements although a slightly higher version was fitted for Le Mans. The mid-mounted engine was cooled thanks to a pair of streamlined air boxes behind the cockpit, hot air being extracted through six horizontal vents located on the rear deck and a bank of 16 vertical on the tail facia. Rear wings were everything you would expect from a mid-sixties Italian sports prototype, bulbous, beautiful and muscular, they left you with the distinct impression this might be a motorcar of serious performance. Bizzarrini kept the P538 bereft of aerodynamic addenda and produced an exceptionally clean design, his work being refined by Neri & Bonacini before further bodywork and mechanical detailing was carried out by Carrozzeria BBM. P538's were then shipped back from Modena and the finishing touches applied in Livorno.

Pictures are of Chassis #002