10 things you didn’t know about...
The BD engine
Walter Hayes, Ford’s dynamic PR chief, was so enthused by the success of the Ford-based FVA F2 engine, that he asked Cosworth to provide a 16-valve/ DOHC road car engine too. The result, the BDA, was totally different to the FVA, and not based on it. It was, most emphatically not, a ‘de-tuned’ version of the FVA – for the cylinder block, cylinder head, bore, stroke, capacity and camshaft drives were all new.
Although Keith Duckworth had designed the original FVA in 1966, it was a senior colleague, Mike Hall, who was totally responsible for the layout of the BDA in 1968. Mike Hall had recently joined Cosworth from BRM, where he had worked on that company’s engines, and the race-tuning of the Lotus- Cortina/ Escort TwinCam engines. Mike was always Ford’s leading ‘road car’ engine designer.
Developed around Ford’s cast iron ‘Kent’ cross-flow cylinder block, the original BDA’s bore and stroke dimensions were 80.96 x 77.62mm, which gave a capacity of 1599cc. When Ford came to use it in the Escort RS1600 road car, for homologation purposes these dimensions were quoted at 80.96 x 77.72mm/1601cc – the larger stroke dimension being the ‘top tolerance’ dimension of the crankshaft machining details. Purely ‘by chance’ (and if you believe that, you’ll believe anything), this put the engine into the 1.6-litre to 2.0-litre class, and the sporting regulations always allowed the capacity to be enlarged towards the top limit of that class. Clever...
The camshaft drive of all BD engines was by internally cogged belt – whereas the FVA had used enmeshed spur gears for the same task. Comparative tests at Cosworth using BD top
ends on the block, with the bore and stroke of an FVA showed virtually no difference in power-tuning potential between them.
Although Cosworth designed, developed, and evolved the entire BD family, they never produced the engines in quantity – though they provided all the complex castings for the cylinder head. Over the years, road-car production was tackled by companies as varied as Harpers of Letchworth, Weslake Engineering, Brian Hart Ltd. or JKF of Easton Neston.
The light-alloy cylinder block version of the BD, first seen in race cars in 1971, was designed by Brian Hart Ltd, not Cosworth. There were two reasons for this – one being to take weight out of the engine, the other being to re-core the block to allow a 90mm cylinder bore to be used on competition types, which provided a 1975cc capacity. Ford first saw the lightalloy prototype in the winter of 1971/1972, instantly adopted it for use in the Escort RS1600, of which road-car derivatives ( still of 1599cc/1601cc) were standardised from the autumn of 1972.
BD types were enormously versatile, in road cars and competition cars. For motorsport use, there were versions of only 1.1-litres (which required the use of the smallest Kent cylinder block), and as large as 2.0-litres (the famous BDG, as used in hundreds, if not thousands, of competition cars). Although series production, which had started in 1970, ended in 1986 (with the RS200 and RS200E), Cosworth continued manufacturing complete cylinder blocks and cylinder heads until the 2010s, though prices had reached astronomic levels.
Road car engines were produced in 1599cc, 1803cc, and 1835cc form, usually with Weber or Dell’orto carburettors, or ( in the case of the RS200) with Ford fuel injection and turbocharging. Works Escorts were usually rallied with Webers, but in later years with Lucas or even Kugelfischer fuel injection.
Against its better judgement, Cosworth was persuaded to produce a turbocharged 1.5-litre F1 engine in 1984, this being loosely based on the BDA power unit, though with a totally different cylinder head and a complex turbo/fuel injection installation. It was not a success, several spectacular test bed blow-ups followed ( one seen ‘live’ on a TV documentary programme), so the project was cancelled – and was succeeded by the 1,000bhp GB V6 turbo.
The final derivative of this engine was the BDT-E, a big-bore turbocharged 2,137cc engine designed completely by Brian Hart Ltd in 1985-1986, with no reference to Cosworth. This was achieved with a ‘stretched’ cylinder block/cylinder centres which allowed space for the bigger bores. The initial 25 engines were intended for use in the RS200E ‘evolution’ car (where, according to sporting regulations, their capacity was 2,992cc!), but the cancellation of Group B meant that this project was cancelled. Approximately 50 BDT-E engines were eventually produced, the most race-tuned types producing 650bhp.