Brabham BT19 - Engine and Transmission

Engine and Transmission

Repco racing engines were designed and built by a small team at a Repco subsidiary, Repco-Brabham engines Pty Ltd, in Maidstone, Australia. Repco's 620 series engine is a normally aspirated unit with eight cylinders in a 'V' configuration. It uses American engine blocks obtained from Oldsmobile's aluminium alloy 215 engine. Oldsmobile's 215 engine, used in the F-85 Cutlass compact car between 1961 and 1963, was abandoned by General Motors after production problems. Repco fitted their own cast iron cylinder liners into the Oldsmobile blocks, which were also stiffened with two Repco magnesium alloy castings and feature Repco-designed cylinder heads with chain-driven single overhead camshafts. The internals of the unit consist of a bespoke Laystall crankshaft, Daimler connecting rods and specially cast pistons. The cylinder head design means that the engine's exhaust pipes exit on the outer side of the block, and therefore pass through the spaceframe before tucking inside the rear suspension, a layout which complicated Tauranac's design work considerably. The engine is water-cooled, with oil and water radiators mounted in the nose.

The 620 engine was light for its time, weighing around 340 lb (154 kg), compared to 500 lb (227 kg) for the Maserati V12, but in 3 litre Formula One form only produced around 300 brake horsepower (220 kW) at under 8000 revolutions per minute (rpm), compared to 330–360 bhp (250–270 kW) produced by the Ferrari and Maserati V12s. However, it produced high levels of torque over a wide range of engine speeds from 3500 rpm up to peak torque of 233 pound feet (316 N·m) at 6500 rpm. Installed in the lightweight BT19 chassis, it was also relatively fuel efficient; on the car's debut Brabham reported that the BT19 achieved 7 miles per gallon (40 L/100 km), against figures of around 4 mpg (70 L/100 km) for its "more exotic rivals". This meant that it could start a Grand Prix with only 35 gallons (160 L) of fuel on board, compared to around 55 gallons (250 L) for the Cooper T81-Maseratis. The engine had one further advantage over bespoke racing engines: parts were cheap. For example, the engine blocks were available for GB£11 each and the connecting rods cost £7 each.

The 740 series unit used in the three races for which the car was entered in 1967 has a different, lighter, Repco-designed engine block. It also has redesigned cylinder heads which, among other improvements, mean that its exhausts are mounted centrally and do not pass through the spaceframe or rear suspension, unlike those of the 620 series. It produced a maximum of 330 bhp (250 kW).

The BT19 was initially fitted with a Hewland HD (Heavy Duty) gearbox, originally designed for use with less powerful 2-litre engines. The greater power of the 3-litre Repco engine was more than the gearbox could reliably transmit when accelerating at full power from rest, with the result that Brabham normally made very gentle starts to avoid gearbox breakages. The HD was later replaced with the sturdier DG (Different Gearbox) design, produced at the request of both Brabham and Dan Gurney's Anglo American Racers team. It later became a popular choice for other constructors.