#Tech – The Cosworth BD engine.

Cosworth was founded in 1958 by Mike Costin and Keith Duckworth. It has become the most successfull engine manufacturer in history. The number of driver and manufacturer titles to its credit in a wide range of formulae with impressive performances in Formula 1, IRL, Champ Car, WRC, sportscars and MotoGP are the best testimony of the capabilities available at their office.

The first ever victory came with the Cosworth tuned Ford 105E Formula Junior engine in 1960 with Jim Clark driving the equipped Lotus 18 to outright win. Later, in 1967, it would introduce the Cosworth DFV V8 in Formula 1 through the Lotus 49. They would set the trend for the coming years with their revolutionar design taking 155 wins in 15 years.

But let’s talk about the most declined engine they’ve build, the Cosworth BD serie.

In 1967 Harley Copp, Walter Hayes and Henry Taylor reached an agreement with Cosworth to develop an engine for Ford of England. The objective was to develop and engine with better performance than the twin-cam Lotus-Ford.

Keith Duckworth was engaged full-time on the DFV engine so Mike Hall took on the design responsibilities. The new engine was based on the Ford Kent block and would use the same basic cylinder head breathing as the earlier FVA 4-cylinder and the V8 DFV.

The agreement between Ford and Cosworth was for the design and development, not the building of engines. Design started in May of 1967 and the first 1600cc engine ran in June of 1968. The BDA means Belt-Drive Series A, which refers to the way the camshafts were driven. When introduced it was the first British engine to use cogged belts to drive the camshafts.

From Cosworth’s perspective the BDA took on a life of its own. In 1970 the BDB version was introduced. This was developed for Ford for use in the Escort RS1600 for rallying. The bore was increased for a capacity of 1700cc. According to Cosworth’s Mike Hall, the BDA just snowballed into the “Meccano set” of engines. By the mid-1970s the various BD engines accounted for over half of Cosworth’s turnover. Modifications were introduced by Cosworth and several other companies. The company continued to produce kits of parts to build up BD engines into the 1980s.

1969, The BDA, 1601cc, 120 HP

Cosworth increased its association with Ford in 1969, by developing a double overhead camshaft (DOHC) 16-valve inline four-cylinder engine for road use in the Ford Escort. Working from the Kent block, Cosworth created a 1,601 cc for homologation purposes. 

The camshafts were driven by a toothed belt, hence the name BDA, literally meaning “Belt Drive, A type”. Running in Group 2 and Group 4 on either rallying or touring car racing, this engine could be enlarged to a maximum of 2,000 cc. 

The nominal homologation at 1,601 cc capacity meant that BDA-engined cars competed in what was usually the top class (1600 cc and up) so were eligible for absolute victories rather than class wins.

1973, The BDG, 1975cc, 275 HP

The BDG was the evolution of the BDE built for Formula 2. The BDF was an improved development of the BDE. In 1973 the BDG was introduced, it featured another increased cylinder capacity and produced 275 bhp. The first versions had a cast iron block, but later engines had an aluminum block.

The BDG had a capacity of 1975cc/120.5 cu in. The compression ratio was 12.0 to 1 for a horse power rating of 280 at 9250 rpm. The cylinder numbering was 1 – 2 – 3 – 4 front to rear with a firing order of 1 – 3 – 4 – 2 .

The BDG became the most commonly used engine from 1973, being used from Formula 2 to the Le Mans sportscars such as the later Chevron B36.

Chevron B36 BDG
Chevron B36 BDG
Type Year Size Output Description
BDA 1969 1601cc 120 Bhp. Belt Drive layout similar to FVA on taller Kent block
BDB 1970 1700cc 200 Bhp. Escort RS1600 rally engine, sold as kits
BDC 1970 1700cc 230 Bhp. Injected BDB for Group 2 Escort RS1600, also kits
BDD 1971 1600cc 200 Bhp. Definitive Formula Atlantic Motor, also kits
BDE 1972 1790cc 245 Bhp. Formula 2 first stretch to 2 litre rules, bigger bore, injection
BDF 1972 1927cc 270 Bhp. Formula 2 next stretch, liners brazed in to cast iron block, very successful
BDG 1973 1975cc 275 Bhp. Formula 2 and rally, development of BDF, later with aluminum block
BDH 1973 1300cc 190 Bhp. Group 2 Sports cars, shorter stroke on shorter block
BDJ 1974 1098cc 150 Bhp. Formula C, short stroke version for SCCA
BDK Unused
BDL experimental turbo
BDM 1975 1599cc 225 Bhp. Formula Atlantic, big valve, injected BDD
BDN 1977 1600cc 210 Bhp. Formula Atlantic, Canadian Atlantic sealed motors this year only, sold as kits
BDO Unused
BDP 1984 1975cc 245 Bhp. Sprint car, aluminum block, BDG bore/stroke, injected, methanol
BDQ Unused
BDR 1983 1601cc 120 Bhp. BDA kits for Caterham Super Sevens, also 1.7 litre and 150, 170 Bhp.
BDT 1981 1778cc 200 Bhp. RS1700T turbo, aluminum block, kits for JQF
1981 1803cc 250 Bhp. RS200 BDT units redesigned, rebuilt, and enlarged
BDT-E 1986 2137cc 500 Bhp. Evolution BDT by Brian Hart, Ltd.

One thought on “#Tech – The Cosworth BD engine.

  1. I think you may be in error with respect to the statement that the BDA was the first UK belt drive production engine – the Vauxhall Slant-4 1.6 and 2 litre engines went into production in Sept 67 whereas the RS1600 Escort replaced the Twin Cam in 68?

    The first US timing belt engine was the I6 in the ’65 Pontiac Tempest (a John DeLorean project!)

    Even before that was the 1961 or 2 Glas (a German brand, later swallowed by BMW) and that was the first production car implementation. However, the construction of the Glas belt was different from the Uniroyal used by GM and upon which all subsequent belts have been based

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