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By 1981 Opel has had a succesful history in rally sport with his Ascona 400. The number relates to the required production number for a particular car model to be accepted for entering the Group 4 rally championship. Because the planned Ascona C was going to be a front wheel driven car, Opel needed a worthy successor for the Ascona 400. Being build on the same platform as the Ascona, the choice for the Manta was obvious.
Originally the Manta would have been homologated for Group 4 rallying in 1981. This required 400 cars to be produced, hence it got named Manta 400. A year later in 1982, FIA changes the rules. Group 4 was changed into Group B and this required only 200 cars to be build. The Manta 400 name was kept as a reference to the Ascona 400. FIA rules stated that manufacures were allowed to produce 20 example cars each year as an evolution on the original production cars. Once accepted, alterations were allowed on each individual car. With this in mind Opel developed a street version first. The idea was to have this car developed into a full production car, leaving room for 20 modified rally evolutions each year. Opel was confident in the homologation process and expected a quick procedure. The first streetlegal prototype of the Manta 400 was presented at the Geneva motorshow of 1981. It featured the standard A400 144Bhp engine. Opel unveales the wide body rally version a few months later in September at the IAA in Frankfurt. On month later, in October production of the street-version finally begins. Pre-orders show that by then the first evolution of competition cars is already sold out. The cars all left the production factory in Antwerp as normal 2.0 GT/E chassis without the engine and drive train, painted in a Polar White finish. From Antwerp they were put onto a train. Destination: Irmscher Germany, were they were customized into a 400 chassis. Because production started before the 1982 facelift, the first 23 Manta 400’s still had the 2 slot airdam in the front. All 1982 and 1983 models were finnished with the 4 slotted airdam following the Manta’s facelift. By the end of 1983, a total of 245 are build by Irmscher. Most of which were used as competion cars.
Looking similar to a GT/E, the street version Manta 400 had some distinguished features. The engine was again being build by the British Cosworth. The 2.0 CIH was replaced with a 2.4l DOHC engine with a Cosworth crossflow 16v head and L-Jetronic fuel injection.
Going back to the Ascona 400, Cosworth were originally given the task of upgrading the existing Opel 16 valve head for the 2.0 CIH engine as it was used for the Kadett C. Lacking the needed power and increasing development costs, forces Opel to drop further improvement of the 16v CIH project. Instead they based the Ascona 400 engine on a 2.3-litres Rekord diesel engine block. Which proved very reliable. Keith Duckworth upgraded it to a 2.4-litres engine and added a high technology 16 valve crossflow cylinder head, based on a design by Cosworth done in 1972. It was capable of runnning at the high revs rallying demanded for. The standard street model delivering 144 Bhp had a Bosch L-Jetronic fitted. Phase 1 as found in the original Ascona 400 had double 45 DCOE Weber carburettors delivering 240 bhp. Later these where upgrade to double 48 Webers in Phase 2 with 261 Bhp and finaly Phase 3 which had double 50 Webers, good for 280 bhp.
The chassis was further developed and modified by Irmscher and housed a 5-link rear axle (taken from the Commodore). It also accomodated rear disc brakes, and vented front discs brakes together with 5-loch wheels. Very quickly rally drivers complained about the car having a lot of under-steer. This was mainly because of the heavy front end of the Manta. To help weight distribution, the engine was moved 6cm backwards, compared to the original fitting. To reduce the total car weight, kevlar doors, bonnet, spoilers, boot lid, mudguards and even lamp holders were used, saving up more than 80kg and reducing the total weight to 960kg. The main problems however would become the rear axle as the engines became more powerful. The axles which were so reliable in the Ascona 400, were reused to reduce development costs. In act a lot of the technology from the Ascona 400 was used on the Manta. With the Manta 400 being much lighter than the Ascona 400, the axle couldn’t take the abuse it had to indure because of the increase in power of the engines.
Opel tested the Manta 400 in all possible conditions to make sure it would fulfill its task. Two years pass and still no homologation was provided. With the engine being in its 3rd phase already, time was running out. Finally, on the 1st of March 1983 – 2 years after is was introduced – FIA comisioners approve the Manta 400 with its Phase 3 engine. After they tested 20 cars, all in rothmans trimm, its registration number is sealed. Its registered at FIA as B-237.
Opel now has 2 months to prepare itself for the Manta’s debug at the Tour de Corse. But it would not be without a bit of luck that the Manta would start in Corsica. Due to some flight problems and bad scheduling, the official papers do not arrive in time to the French Island. Rally officials refuse to enter the Manta in the race without them. After much debat and apparently as the story goes, a bit of champagne in the Rothmans vip area. Team manager Jochen Berger convinces the FIA president and the organisation to enter the Manta’s, under the condition they would provide the papers later that weekend. A fax from German head quarters acted as a backup.
Unfortunatly for Guy Frequelin though, the car lasted only 100 miles before the head gasket failed. The same weekend, Jimmy McRae gave another Manta 400 its debut in the Welsh Rally and was far more successful. He could have taken second place until he went off the road. He finally finished sixth.
According the Jochen Berger, the Manta arrived 2 years to late. Being a rear wheel drive car, made it difficult to compete in with the 4wd power monsters of Group B such as the Audi Quatro and Lancia’s. Not less than a year after it’s debut in France, Opel started a four wheel drive Manta project in cooperation with Furguson, a British company specialised in all wheel drive technology. One prototype was presented to the press in Sweden. Test driven by Henri Toivononen and Ari Vatanen, it proved to be more controllable than the Audi Quattro. A visco coupling was used to transmit 36% of the power to the front wheels. It also had an improved acceleration. Tested on wet grass, it could accelerate 5s faster than a regular car. As promissing as first test were, being cosidered a new model, it had to be submitted again for homologation. Since Opel didn’t have the time nor money do so, the whole project was canceled. The prototype 4WD car was reused in rallying as a normal 2 wheel drive Manta in the Acropolis later that year.
The Manta 400 would live a short Group B rally live as in 1986, during the Tour of Corsica, Toivonen crashes his Lancia S4 and unfortunatly dies. The gravity of the accident causes the FIA to ban Group B from the competition as of then.
Not to be mistaken for the Manta i200 made by Irmscher, Opel also announced a second homologation model for Group B rallying in 1984. With FIA rules requiring 200 cars to be produced, the Manta 200 was created as the successor for the Ascona 2000. Just like the i200, it was based on a GT/E with a 2.0 CIH engine. The difference was that instead of the original electronic fuel injection, it was homologated with double 48 Weber carburattors and a “Swedenhead”. The head was build by the Swedisch motorsports departement of GM Sweden under supervision of Ragnar Eklund. Its development shows records dating to the late 60’s were it was used for competion Opel Records. The biggest difference with a normal head lies in the bigger size of the in- and outtake channels. It also featured rear disc breakes, and could be ordered with the optional 5-loch axles (it was presented this way in the brochure). With additional tuning upgrades it could reach 186 Bhp and 206 Nm torque. Total weight of the car was reduced to 990 kg.