Editing Cosworth DFV (section)

==Variants==

===DFW===
The first variant produced from the DFV was a reduced-capacity unit for the [[Australia]] and [[New Zealand]]-based [[Tasman Series]] races of 1968–69. The changes between the DFV and DFW specification were limited to a reduced [[Stroke (engines)|stroke]], taking capacity to 2491&nbsp;cc and reducing power output from the DFV's {{cvt|420|bhp|kW PS|0}} in {{f1|1967}} to ~{{cvt|360|bhp|kW PS|0}} (after winning the [[Surfers Paradise International Raceway|Surfers Paradise]] round of the [[1968 Tasman Series]], [[Jim Clark]] told that other than lacking the top end power of the DFV, there really wasn't a big difference in performance between the DFV and DFW).<ref name="motorsport02">Robson, G. (2007) Cosworth DFV: Horses for courses. ''Motor Sport'', '''83(7)''', 44–48.</ref><ref>[https://www.youtube.com/watch?v=dpq-Va4DVD8 1968 Tasman Series Rd 5 Full Race]</ref> In Tasman Series racing, other 2.5L engines that the DFW was generally up against were the Australian made [[Repco V8]], the [[Alfa Romeo]] V8 (as seen in Alfa's [[Alfa Romeo Tipo 33|T33/2]] [[World Sportscar Championship|endurance racing]] [[Sports car racing|sports car]]), a 2.5L version of the [[BRM V8 engine]], the 2.4L [[Ferrari Dino engine|Ferrari V6]], and the older 2.5L [[Coventry Climax FPF]], the Australian versions of which were actually made under licence by Repco. On tighter tracks such as [[Wigram Airfield Circuit|Wigram]] (NZ) and [[Warwick Farm Raceway|Warwick Farm]] (AUS), there was also the smaller capacity ({{cvt|1598|cc|L|1|order=flip}}) [[Cosworth FVA]] to contend with.

The DFW is was the smallest capacity variant of the DFV that was officially produced by Cosworth. The engine was a direct replacement for its DFV parent in [[Lotus 49]]s. The small engine proved just as competitive as the larger version; and Jim Clark took four race victories in 1968, though Clark also noted after the Surfers round on a track that suited higher powered cars, the lower power of the DFW was not quite suited to the full size Lotus 49T built for Formula One (highlighting the lack of top end punch along with the heavier F1 car, for the first half of the Surfers race Clark was in a dogfight for the lead with the smaller, more nimble [[Formula 2]] chassis [[Dino 246 Tasmania|Ferrari]] of [[Chris Amon]] and its {{cvt|285|bhp|kW PS|0}} V6 engine, a scenario they would repeat when Clark beat Amon by just 0.1 seconds to win the [[1968 Australian Grand Prix]] at another noted power circuit, [[Sandown Raceway|Sandown]] in [[Melbourne]]). The DFW also saw one win for [[Piers Courage]] driving a [[Brabham BT24]] for [[Frank Williams Racing]], and two victories for [[Jochen Rindt]] in the [[1969 Tasman Series]] (Rindt had replaced Clark at [[Team Lotus|Lotus]] after the [[Scottish people|Scotsman]]'s tragic death in a Formula 2 race at [[Hockenheim]] just over a month after winning the Tasman in 1968). [[Derek Bell (racing driver)|Derek Bell]] drove a DFW version of the [[Brabham BT26]] to second place in the [[1970 New Zealand Grand Prix]], and for the 1971 Tasman Series previous champion [[Chris Amon]] drove a DFW-powered version of his current Formula One chassis, the [[March 701]], to another podium finish, but in both years the Formula One-derived engine was largely outmatched by [[Formula 5000]] entrants with their 5.0L Repco-[[Holden V8 engine|Holden]] and [[Chevrolet small-block engine (first- and second-generation)|Chevrolet]] V8's producing some {{cvt|480-500|bhp|kW PS|0}} in 1971.

After the demise of the 2.5L component of the [[Tasman Formula]] following the 1971 season, the four DFW engines were converted back to DFV specification.

===Formula One===
The DFV had three major upgrades over its life in the top formula, with the development of first the DFY and then the DFZ, followed by a major redesign to produce the final DFR type.

====DFY====
{{Infobox automobile engine
| name = [[Cosworth]] DFY<ref name="Engine Ford Cosworth • STATS F1">{{cite web |url=https://www.statsf1.com/en/moteur-ford-cosworth.aspx |title = Engine Ford Cosworth • STATS F1}}</ref>
| image = 
| manufacturer = {{flagicon|UK}} [[Ford Motor Company|Ford]]-[[Cosworth]]
| production = 1983–1985
| configuration = [[V8 engine|V8]], [[naturally aspirated|naturally-aspirated]], 90° cylinder angle
| displacement = {{cvt|2992.6|cc|L|1|order=flip}}
| bore = {{cvt|90|mm|in|1|lk=on}}
| stroke = {{cvt|58.8|mm|in|1|lk=on}}
| block = [[Aluminium]] alloy
| head = [[Aluminium]] alloy
| valvetrain = 32-valve, [[DOHC]], four-valves per cylinder
| power = {{cvt|510-530|hp|kW|0|lk=on}}
| torque = {{cvt|280|lbft|Nm|0|lk=on}}
| oilsystem = Dry sump
| weight = {{cvt|150|kg|lb|0|lk=on}}
| fuelsystem = Electronic and mechanical indirect fuel injection
| fueltype = [[Gasoline]]
}}
With the introduction of turbocharged engines towards the end of the 1970s, Cosworth's naturally aspirated DFV began to lose its predominance. In an attempt to recover some of the performance deficit Cosworth designer [[Mario Illien]] reconfigured the cylinder aspect ratio to allow the engine to rev more freely, and combined this with a narrow-angle valve set-up and [[Nikasil]] Aluminium liners. The changes upped power output to ~520&nbsp;bhp,<ref name="motorsport02" /> and between 11000-12000&nbsp;RPM but this was not sufficient to keep pace with the turbo cars at most tracks, and it was only through a modicum of luck that [[Michele Alboreto]] was able to take what would prove to be the DFV-family's final F1 victory, at the [[1983 Detroit Grand Prix]]. The DFY lived on with back-marker teams until the end of the {{F1|1985}} season, when Cosworth switched their efforts to supporting the new turbocharged Ford GBA V6.

====DFZ====
{{Infobox automobile engine
| name = [[Cosworth]] DFZ<ref name="Engine Ford Cosworth • STATS F1"/>
| image = 
| manufacturer = {{flagicon|UK}} [[Ford Motor Company|Ford]]-[[Cosworth]]
| production = 1987–1988
| configuration = [[V8 engine|V8]], [[naturally aspirated|naturally-aspirated]], 90° cylinder angle
| displacement = {{cvt|3494|cc|L|1|order=flip}}
| bore = {{cvt|90|mm|in|1|lk=on}}
| stroke = {{cvt|68.65|mm|in|1|lk=on}}
| block = [[Aluminium]] alloy
| head = [[Aluminium]] alloy
| valvetrain = 32-valve, [[DOHC]], four-valves per cylinder
| power = {{cvt|575-590|hp|kW|0|lk=on}}
| torque = {{cvt|320|lbft|Nm|0|lk=on}}<ref name="spicerparts.com">{{cite web |url=https://spicerparts.com/calculators/horsepower-torque-calculator |title = Horsepower and Torque Calculator{{!}} Spicer Parts}}</ref>
| oilsystem = Dry sump
| weight = {{cvt|155|kg|lb|0|lk=on}}
| fuelsystem = Electronic and mechanical indirect fuel injection
| fueltype = [[Gasoline]]
}}
The announcement at end of the {{F1|1986}} season that turbocharged cars would be banned from {{F1|1989}}, and the introduction of the [[Jim Clark Cup]] and [[Colin Chapman Trophy]] championships for naturally aspirated cars for {{F1|1987}}, prompted Cosworth to revive their elderly engine design. This resulted in the DFZ, essentially an updated version of the final DFY design. However, the capacity increase for the new 3.5L [[naturally aspirated]] formula running alongside the 1.5L turbos in 1987 allowed Cosworth to increase the power output of the unit to {{cvt|575|bhp|kW PS|0}}.<ref name="motorsport02" /> The engine was intended as a temporary measure to tide smaller teams over until the turbos were banned at the end of the {{f1|1988}} season. [[Tyrrell Racing|Tyrrell]], [[Automobiles Gonfaronnaises Sportives|AGS]], [[March Engineering|March]], [[Lola Cars|Lola]] and [[Enzo Coloni Racing Car Systems|Coloni]] chassis were all powered by Cosworth in 1987. [[Jonathan Palmer]] of Tyrrell eventually won the drivers' Jim Clark Cup, and his team took the constructors' laurels in the Colin Chapman Trophy. The engine remained in service with minor teams until the end of 1988 and development saw a slight power increase to {{cvt|590|bhp|kW PS|0}}. The DFZ did not race in Formula One beyond 1988 as the general release of the DFR engine made it obsolete.

The engine did however have a second brief lease of life in sportscar racing, when the FIA announced plans to transition towards using 3.5&nbsp;L F1-style engines in [[Group C]] in the early 1990s. In 1990 [[Spice Engineering]] adapted its existing Group C design to take a 3.5L DFZ instead of the previously used 3.3&nbsp;L DFL engine. However the new engine caused significant problems due to vibration, which resulted in the breakage of components and a significant increase in running costs - [[Gordon Spice]] estimated that the DFZ-powered car was about four times more expensive to run than the DFL-engined one.<ref>{{cite web |url=http://www.autosport.com/premium/feature/4734/the-death-of-group-c/ |title=The death of Group C |last1=Cooper |first1=Adam|date=24 August 2012 |website=[[autosport.com]] |access-date=2 April 2016}}</ref> The DFZ was successfully used in FIA Cup class racing in 1992, with that low-powered class being the last appearance of the DFV family in sportscar racing.

====DFR====
{{Infobox automobile engine
| name = [[Cosworth]] DFR<ref name="Engine Ford Cosworth • STATS F1"/>
| image = 
| manufacturer = {{flagicon|UK}} [[Ford Motor Company|Ford]]-[[Cosworth]]
| production = 1988–1993
| configuration = [[V8 engine|V8]], [[naturally aspirated|naturally-aspirated]], 90° cylinder angle
| displacement = {{cvt|3494|cc|L|1|order=flip}}
| bore = {{cvt|90|mm|in|1|lk=on}}
| stroke = {{cvt|68.65|mm|in|1|lk=on}}
| block = [[Aluminium]] alloy
| head = [[Aluminium]] alloy
| valvetrain = 32-valve, [[DOHC]], four-valves per cylinder
| power = {{cvt|580-630|hp|kW|0|lk=on}}
| torque = {{cvt|320-400|lbft|Nm|0|lk=on}}<ref name="spicerparts.com"/>
| oilsystem = Dry sump
| weight = {{cvt|155|kg|lb|0|lk=on}}
| fuelsystem = Electronic indirect fuel injection
| fueltype = [[Gasoline]]
| predecessor = [[Cosworth GBA]]
| successor = [[Ford-Cosworth HB engine|Ford-Cosworth HB]]
}}
From {{f1|1987}} [[Benetton Formula|Benetton]] had been operating as the works Ford team, essentially taking over the role from the now defunct [[Haas Lola]] team. With the abandonment of turbocharging it was clear that the venerable DFV/Y/Z design was nowhere near being competitive with far newer offerings from [[Honda F1|Honda]] and [[Renault F1|Renault]] who were building [[V10 engine]]s for 1989 and beyond, and [[Scuderia Ferrari|Ferrari]] who were building what they knew, a [[V12 engine|V12]] ([[Lamborghini]] entered F1 in 1989 and like Ferrari, also went down the [[Lamborghini V12 engine|V12]] path). To counter this, drastic changes were made for the DFR of 1988. Although superficially a DFV-design, almost the only feature carried over from previous versions into the DFR was the basic 90° V8 engine architecture. The DFR became available to all customers in 1989, with the Benetton team also using this engine until the [[1989 British Grand Prix]]. The DFR struggled on until the 1991 season finally being eclipsed by the higher revving abilities of new [[pneumatic valve gear]] engines such as the HB, and was last used in that year's Australian Grand Prix by the Footwork, Fondmetal, Larrousse and Coloni teams, nearly a quarter of a century after the DFV's first race. By the time of its demise, continued improvement had pushed the DFR power output to nearly {{cvt|630|bhp|kW PS|0}},<ref name="motorsport02" /> 60% higher than the original 1967 DFV.

The DFR enjoyed success in 1988 with Benetton. The team was the best performed non-turbo team of the season finishing third in the Constructors' Championship behind Ferrari (turbo) and the all-conquering [[McLaren]]-Honda. [[Thierry Boutsen]] recorded five podium finishes and [[Alessandro Nannini]] scored two podiums. The DFR was also the most powerful non-turbo of the season with a reported {{cvt|620|bhp|kW PS|0}}. This compared to the 590 of the DFZ and the new [[Judd (engine)#CV|Judd]] V8 with a reported {{cvt|600|bhp|kW PS|0}}. This still lagged behind the Honda and Ferrari turbos which were producing over {{cvt|650|bhp|kW PS|0}} each.

The 3.5 L DFR engine was later used in the [[Allard J2X-C]] [[Group C]] [[sports car racing|sports car]], in 1992.<ref>{{cite web |url=https://www.ultimatecarpage.com/car/3532/Allard-J2X-C.html |title = 1992 - 1993 Allard J2X-C - Images, Specifications and Information}}</ref><ref>{{cite web |url=https://www.supercars.net/blog/1992-allard-j2x-c/ |title = 1992 Allard J2X-C {{!}} Allard {{!}} SuperCars.net}}</ref><ref>{{cite web| url = https://drivetribe.com/p/cutting-edge-1992-allard-j2x-c-Fl-f8egMTuig2wNXM7ON_w?iid=RWXtNxoxRguD-L45-2SdRA| title = Cutting Edge - 1992 Allard J2X-C| access-date = 2021-11-19| archive-date = 2021-11-19| archive-url = https://web.archive.org/web/20211119084011/https://drivetribe.com/p/cutting-edge-1992-allard-j2x-c-Fl-f8egMTuig2wNXM7ON_w?iid=RWXtNxoxRguD-L45-2SdRA| url-status = dead}}</ref><ref>{{cite web |url=http://www.mulsannescorner.com/allardj2x.html |title = Mulsanne's Corner: 1992-1993 Allard J2X}}</ref><ref>{{cite web |url=https://www.conceptcarz.com/z19754/allard-j2x-c.aspx |title = 1992 Allard J2X-C {{!}} conceptcarz.com}}</ref>

===North American series===
{{Main|Ford-Cosworth Indy V8 engine}}
[[File:Cosworth DFX engine.jpg|thumb|right|200px|Cosworth DFX]]
[[File:CosworthDFSV8engine.JPG|thumb|right|200px|Cosworth DFS]]

====DFX====
{{Infobox automobile engine
|name=[[Cosworth]] DFX<ref>{{Cite web|url=https://books.google.com/books?id=y-MDAAAAMBAJ&q=cosworth+dfx+engine+rpm&pg=PA76|title = Popular Mechanics|date = May 1987|publisher = Hearst Magazines}}</ref><ref>{{Cite web|url=https://www.museumofamericanspeed.com/cosworthindyengine.html|title = Cosworth DFX Indy Engine}}</ref>
|manufacturer={{flagicon|UK}} [[Ford Motor Company|Ford]]-Cosworth
|production=1976–1987
|configuration=90° [[V8 engine|V8]]
|bore={{cvt|85.67|mm|in|lk=on}}
|stroke={{cvt|57.3|mm|in|0|lk=on}}
|displacement={{cvt|2643|cc|L|1|order=flip}}
|valvetrain=32-valve, [[DOHC]], four-valves per cylinder
|power={{cvt|720-840|hp|kW|0|lk=on}}
|torque= {{cvt|340-490|lbft|Nm|0|lk=on}}<ref name="spicerparts.com"/>
|turbocharger=[[Cosworth]]
|oilsystem=Dry sump
|fuelsystem=[[Electronic fuel injection]]
|compression= 11.2:1
|fueltype=[[Gasoline]]
}}
A 2.65&nbsp;L [[turbocharged]] version of the DFV was developed privately by the [[Vels Parnelli Jones]] team for the 1976 [[United States Automobile Club|USAC]] [[IndyCar]] season, in the face of opposition from Duckworth.<ref name=DFXfiles>{{Cite magazine|author= Kirby, Gordon |title= The DFX Files |url= https://www.motorsportmagazine.com/archive/article/march-2013/115/dfx-files |date= March 2013 |magazine= [[Motor Sport (magazine)|Motor Sport]] |volume= 89 |issue= 3 |pages= 114–118 |access-date= 26 September 2018 }}</ref> The Parnelli-Cosworth car took its first victory at the [[1976 Pocono 500]], the fifth race of the season, driven by [[Al Unser]].<ref name=DFXfiles /> Unser and his Cosworth-powered Parnelli took two further victories before the end of the year, in Wisconsin and Phoenix, and finished the championship in fourth position.

Duckworth had been a guest of the Vels Parnelli team during the Pocono victory, as [[Parnelli Jones]] and [[Vel Miletich]] wanted to establish the team as the North American distributor for the turbocharged, Indycar-specification engine.<ref name=DFXfiles /> However, shortly after the maiden race victory Cosworth poached two key engineers from the Parnelli team and set up facilities in [[Torrance, California]], to develop and market the engine themselves.<ref name=DFXfiles /> Henceforth it became known as the '''DFX'''. It went on to dominate [[American Championship car racing|American Indy car]] racing in much the same way the DFV had dominated Formula One. The engine won the [[Indianapolis 500]] ten consecutive years from 1978 until 1987, as well as winning all USAC and [[Champ Car|CART]] championships between 1977 and 1987 except for one. For a brief time in the early 1980s, some of the DFX engines were [[Rebadging|badged]] as [[Ford Performance|Ford]]s. The DFX powered 81 consecutive Indy car victories from 1981 to 1986, and 153 victories total. By the time it was replaced, the DFX was developing over {{cvt|840|bhp}}.<ref name="motorsport02" />

====DFS====
In 1986 [[General Motors|GM]] financed the British [[Ilmor]] firm to build a competitor to the DFX in [[American Championship car racing|American Indy car]] racing. [[Mario Illien]]'s [[Ilmor|Ilmor-Chevrolet Indy V-8]], which owed not a little to the DFY of five years earlier, quickly took over dominance of the sport.

Ford responded by commissioning Cosworth to redesign the DFX to include a number of DFR improvements. In 1989, they introduced an updated "short [[Stroke (engine)|stroke]]" version of the Indy car engine which would be referred to as the "'''DFS'''" ("S" for ''short stroke'').,<ref>{{cite news |url=https://www.latimes.com/archives/la-xpm-1989-03-09-sp-1544-story.html |first=Shav |last=Glick |title=A Cosworth Comeback Is Key to Rahal Hopes |date=9 March 1989 |newspaper=Los Angeles Times |access-date=13 October 2011}}</ref> and the [[Nikasil]] Aluminium liners, adopted on DFY in 1983.

The engine was fielded by two teams in its first season: Kraco Racing ([[Bobby Rahal]]) and [[Dick Simon Racing]] ([[Arie Luyendyk]]), and its development was an effort to regain dominance of the sport. At [[1989 Indianapolis 500|Indy]], neither car qualified in the front two rows, but both started in the top ten. On race day, both drivers dropped out with engine failures. Rahal won one race in 1989 at the [[Meadowlands Grand Prix|Meadowlands]]. However, the Kraco team merged with [[Galles Racing|Galles]] at season's end, dropped the program, and switched to Chevrolets.

In 1990, the factory development was continued by [[Scott Brayton]] and [[Dominic Dobson]],<ref>{{cite news |url=https://www.latimes.com/archives/la-xpm-1990-05-24-sp-380-story.html |first=Shav |last=Glick |title=11 Buicks Will Have a Race of Their Own in Indy 500 |date=24 May 1990 |newspaper=Los Angeles Times |access-date=13 October 2011}}</ref> but neither won any races. The engine was utilized by other CART teams in 1991–1992, and was retired after the introduction of the [[Ford-Cosworth Indy V8 engine|Ford Cosworth XB]] with only one victory, that being Rahal's in 1989.

===DFL===
{{Infobox automobile engine
| name = [[Cosworth]] DFL<ref>{{cite web |url=http://tech-racingcars.wikidot.com/cosworth-dfl-evolution |title = Cosworth DFL Evolution (1981) - Racing Cars}}</ref><ref>{{cite web |url=http://tech-racingcars.wikidot.com/cosworth-dfl |title = Cosworth DFL (1981) - Racing Cars}}</ref><ref>{{Cite web|url=https://books.google.com/books?id=-uMDAAAAMBAJ&dq=ford+c100+group+c+engine+specs&pg=PA160|title = Popular Mechanics|date = January 1986|publisher = Hearst Magazines}}</ref>
| image = 
| manufacturer = {{flagicon|UK}} [[Ford Motor Company|Ford]]-[[Cosworth]]
| production = 1981–1984
| configuration = [[V8 engine|V8]], [[naturally aspirated|naturally-aspirated]], 90° cylinder angle
| displacement = {{cvt|3954.4|cc|L|1|order=flip}}<br />{{cvt|3298|cc|L|1|order=flip}}
| bore = {{cvt|90|mm|in|1|lk=on}}
| stroke = {{cvt|77.7|mm|in|1|lk=on}}<br>{{cvt|64.8|mm|in|1|lk=on}} 
| block = [[Aluminium]] alloy
| head = [[Aluminium]] alloy
| valvetrain = 32-valve, [[DOHC]], four-valves per cylinder
| power = {{cvt|490-700|hp|kW|0|lk=on}}
| torque = {{cvt|340-510|lbft|Nm|0|lk=on}}<ref name="spicerparts.com"/>
| oilsystem = Dry sump
| compression = 12.0:1-12.5:1
| fuelsystem = Electronic indirect fuel injection
| fueltype = [[Gasoline]]
}}
In 1981 a variant of the DFV named the DFL (for ''long-distance'') was produced specifically for use in the new [[Group C]] [[sports car racing]] class. The engine was modified to larger capacity {{convert|3298|cc|cuin|1|abbr= on}} and {{convert|3955|cc|cuin|1|abbr= on}} versions (despite technically being 4.0 Litres, the 3955 cc version was always referred to as a 3.9 Litre), both with wider bore and longer stroke dimensions than the standard DFV. Both versions were plagued by reliability issues worse than with the DFV they were supposed to replace. The 3.3&nbsp;L version powered [[Jean Rondeau (racing driver)|Rondeau]] to the second points standing in the [[World Sportscar Championship]] season of 1982, but it was insufficiently reliable to be competitive in the longer events. Thereafter, the 3.3&nbsp;L DFL in the C1 class was unsuccessful, with those who managed to actually finish invariably ending up behind C2 cars. The new fuel-restricted C Junior (C2) class in 1983 opened a niche for successful use of the 3.3&nbsp;L version, where low power tuning brought its reliability to a level where it could succeed. In the C2 category it powered many privateer cars, mostly [[Spice Engineering|Spices]] and [[Tiga Race Cars|Tigas]], to class victories around the world, including five at the [[24 Hours of Le Mans]] between 1985 and 1990. The 3.9&nbsp;L version never achieved the same success as its smaller sibling, with most users finding incurable engine vibrations and it was out of competition use by 1985. It was used to power the famous [[Ford Supervan]] and [[Ford Supervan 2|Supervan 2]] promotional projects, as well as the Australian designed and built [[Romano WE84]] in the [[Australian Sports Car Championship]], which ran the 3.0&nbsp;L DFV in the championship before upgrading to the 3.9&nbsp;L DFL for the [[1984 World Sportscar Championship season|1984 World Endurance Championship]] round at the [[Sandown Raceway]] in [[Melbourne]], where it finished 100 laps behind the class winner.

In August 1982, a turbocharged version of this engine was tested briefly on the [[Brands Hatch]] Circuit mounted on a [[Ford C100]].<ref>{{cite web |url=https://www.ultimatecarpage.com/spec/7284/Ford-C100.html |title = 1981 - 1982 Ford C100 Specifications - Ultimatecarpage.com}}</ref><ref>{{cite web |url=http://tech-racingcars.wikidot.com/ford-c100 |title = Ford C100 group C (1981) - Racing Cars}}</ref><ref>{{cite web |url=https://www.classicfordmag.co.uk/features/fords-forgotten-history-the-le-mans-c100/ |title=Ford's Forgotten History: The Le Mans C100 {{!}} Classic Ford Magazine |access-date=2021-11-19 |archive-date=2021-11-19 |archive-url=https://web.archive.org/web/20211119105508/https://www.classicfordmag.co.uk/features/fords-forgotten-history-the-le-mans-c100/ |url-status=dead }}</ref>

===P86 750cc motorcycle engine===
{{main|Norton Challenge P86}}
In 1973 [[Norton Motorcycle Company|Norton]] approached Cosworth to help build a new engine that could be used for both street and racing motorcycles. The idea was to create a 750-cc parallel-twin version of the DFV, with liquid-cooling, 4-valve head, dual overhead cams and flat combustion chambers.<ref name="Cormier">{{cite web |last1=Cormier |first1=Jason |title=Norton P86 750 Challenge - Norton's Last Gasp |url=https://www.odd-bike.com/2013/02/norton-p86-750-challenge-nortons-last.html |website=www.odd-bike.com |access-date=14 March 2019}}</ref> Expected power was to be 65–75{{nbsp}}hp for road bikes, and at least 100{{nbsp}}hp for the racing bikes.<ref name="Cormier" />

The P86 had a bore of 85.6{{nbsp}}mm and a stroke of 64.8{{nbsp}}mm, giving a capacity of 746{{nbsp}}cc.<ref name="Cormier" /> A timing belt was used to drive the cams, rather than the gear train used on the DFV.<ref name="Cormier" /> The P86 shared the same combustion chamber, head designs, pistons and rods from the DFV.<ref name="Cormier" />

Norton specified that the P86 must run through a single carburettor source, which led to a 360° firing interval, with both pistons rising and falling as a pair.<ref name="Cormier" /> As this led to increased vibration, a dual counterbalancing system was developed, in conjunction with a heavy flywheel.<ref name="Cormier" /> In an engine weighing 195{{nbsp}}lb, 75{{nbsp}}lb of that was a rotating mass inside, which was a lot of inertia to be driven.<ref name="Cormier" />

The P86 had downdraught ports like the DFV, but used two Amal carburettors, rather than the fuel injection of the DFV. The carburettors and angle in relation hampered fuel delivery and power output.<ref name="Cormier" />

Dyno testing showed that the P86 developed 90{{nbsp}}hp, down on the projected 100{{nbsp}}hp, while the massive amount of rotating weight inside the engine (counter balancers and flywheel) hindered throttle response.<ref name="Cormier" /> The overall weight of the engine meant that it was never going to be as light as equivalent engines from Japanese manufacturers. The belt driven timing system was inaccurate, while the belts themselves were fragile and prone to breaking.<ref name="Cormier" />

The P86 was fitted in a Norton 'frameless' chassis that made its racing debut in 1975, but results were poor, due to the lack of power. When Norton Villiers Triumph was split up in 1976, an offshoot company called NVT Engineering disbanded the testing and racing departments, and the existing bikes and spare engines (30 in total) were sold off.<ref name="Cormier" />

The P86 made a brief comeback 10 years later at the 1986 Battle of the Twins, held at the [[Daytona International Speedway]]. The Quantel entry featured one of the surviving P86 engines – reworked, fitted with fuel injection and bored out to 823{{nbsp}}cc.<ref name="Cormier" /> Ridden by Paul Lewis, the Quantel finished 2nd, and would win the event in 1988 ridden by Roger Marshall.<ref name="Cormier" /><ref>{{Cite web |last=Lawrence |first=Larry |date=2018-05-09 |title=2018/05/article/archives-when-cosworth-won-at-daytona/ |url=https://www.cyclenews.com/2018/05/article/archives-when-cosworth-won-at-daytona/ |access-date=2023-02-23 |website=www.cyclenews.com}}</ref>