For the 1966 Formula One season the Fédération Internationale de l'Automobile (FIA) doubled the limit on engine capacity to 3 litres (183 cu in).

Climax abandoned the FWMW's development before the end of 1965, their existing FWMV V8 engines proving powerful enough to propel Jim Clark's Lotus 33 to seven wins and the drivers' championship.

Repco delivered the first example of the new engine to the team's headquarters in the United Kingdom in late 1965,[7] just weeks before the first Formula One race to the new regulations, the non-championship South African Grand Prix on 1 January 1966.

The company's reputation rested in part on BRO – effectively the official 'works' team – using the same technology as its customers, for whom ease of repair was a significant consideration.

[11][b] The bodywork of the BT19 is glass-reinforced plastic, finished in Brabham's usual racing colours of green with gold trimming around the nose.

[9] Although the science of aerodynamics would not greatly affect Formula One racing until the 1968 season, Tauranac had been making use of the Motor Industry Research Association wind tunnel since 1963 to refine the shape of his cars.

[12] Brabham has attributed the car's "swept-down nose and the upswept rear lip of the engine cowl" to Tauranac's "attention to aerodynamic detail".

That is, the bulky springs and dampers are mounted in the space between the wheels and the bodywork, where they interfere with the airflow and increase unwanted aerodynamic drag.

Tauranac persisted with this apparently conservative approach based on wind tunnel tests he had carried out in the early 1960s, which indicated that a more complicated inboard design, with the springs and dampers concealed under the bodywork, would provide only a 2% improvement in drag.

The front uprights, the solid components upon which the wheels and brakes are mounted, were modified from the Alford & Alder units used on the British Triumph Herald saloon.

The rear suspension is formed by a single top link, a reversed lower wishbone and two radius rods locating cast magnesium alloy uprights.

The internals of the unit consist of a bespoke Laystall crankshaft, Chevrolet or Daimler connecting rods and specially cast pistons.

The 620 engine was light for its time, weighing around 340 lb (154 kg), compared to 500 lb (227 kg) for the Maserati V12,[17] 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.

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.

[20] The BT19 was initially fitted with a Hewland HD (Heavy Duty) gearbox, originally designed for use with less powerful 2-litre engines.

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.

Similar problems stopped the car on the second lap of the Syracuse Grand Prix in Sicily, but at the International Trophy at the Silverstone circuit, Brabham set pole position, a new lap record, and led the whole race to win ahead of 1964 champion John Surtees in a 3-litre works Ferrari.

After 12 laps Bandini pulled away from Brabham, eventually by over 30 seconds, but when the Italian car was delayed by a broken throttle cable on lap 32, Brabham cruised to the finish to win from Parkes and become the first man to win a Formula One World Championship race in one of his own cars.

The race was held on the tight and twisting Brands Hatch circuit, the track made slippery by oil leaking from other cars and by drizzle.

[27] At the next championship round, the Dutch Grand Prix, Brabham reported the low speed Zandvoort circuit to be "even more oily and treacherous than Brands.

As at Reims, Brabham successfully slipstreamed the race leaders early on, but an oil leakage stopped the car after 8 laps.

[32] Commenting on the reasons for the unexpected competitiveness of the 1966 Brabham-Repcos in Formula One, motorsport historian Doug Nye has suggested that they "could score on weight over the more powerful Ferrari, BRM, Cooper-Maserati, Eagle-Weslake and Honda in their undeveloped forms, and on sheer 'grunt' over such interim stop-gap cars as the nimble 2-litre Climax and BRM V8-engined Lotus 33s and BRMs.

"[33] BT19 also competed in the final two races of the 1965/66 Tasman Series in Australia, which was run to the pre-1961 Formula One regulations, including an engine capacity limit of 2.5 litres.

In 1986, Automotive Components Ltd. (ACL) was formed by the management buyout of Engine Parts Group, which included the transfer of the BT19 to the new company.

[36] In 2002, at the inaugural Speed on Tweed historic meeting at Murwillumbah, Brabham, then 76, commented: "It's been a wonderful car over the years and it's been very well looked after and it's a pleasure to come and drive it.