Unlike Porsche, Forghieri already had a strong 3-litre engine, the new flat-12, introduced in F1 in 1970. Theoretically you can’t run an F1 engine in a sports car, at least not without detuning it substantially. But Ferrari’s unique set up, the recent injection of cash from Fiat’s partial buyout, and the Old Man’s drive for success in all spheres allowed it to spend whatever time and money were necessary to turn its F1 engine into an enduro unit.
Forghieri’s central aim in flattening the iconic V to a boxer flat-12 was to lower the centre of gravity and offer clean airflow to the F1 car’s rear wing. With its four chain-driven overhead camshafts, the 48-valve unit was relatively wide but short, aided by using only four main bearings, which also reduced friction. By the time it went into the sports car the engine had upgraded to a bigger bore, shorter stroke spec with large valves, offering more power and revs. Also the Lucas injection fuel metering unit had moved from the side to the top of the block to improve access, crucial in endurance races. Screwing back the F1 tune by some 40 horses left the PB with about 440bhp, with the red line arriving almost two grand earlier than the GP car at 10,800rpm.
This refined power source sat in, or rather hung from, an ally-clad spaceframe with an extension over the engine to share the suspension loads. On each side of the cockpit were wide sponsons; a main fuel tank filled the left one to counterbalance the driver, with a smaller reserve on the right. Unusually there was a sight gauge for the oil set into one sill. Large surface ducts scooped air to vertical radiators ahead of the rear wheels with the oil cooler crouching on the clutch housing.
Regazzoni heads the charge at Brands Hatch in 1972
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If there was a snag in the boxer layout it was that the heads, the rear suspension, and the underslung exhaust pipes all wanted to share the same space, so the sports car copied the F1 rear suspension, with reversed lower wishbone locating on the five-speed gearbox, single top link and twin radius arms. Up front the usual double wishbones sufficed, with the steering rack mounted above the driver’s knees. With these commonalities it was inevitable that the PB was labelled a ‘two-seater grand prix car’ – which didn’t do Maranello’s image any harm at all. To clothe its new machine, Ferrari abandoned the lovely curves of the 312P for a minimal hard-edged, slab-sided form which, with its cutaway tail kick-up, still has a chunky appeal. And thanks to magnesium suspension components it came in under the new weight limit.
