The history of the development of the Opel CIH engine, 1966-1993.
The new era
Opel's Camshaft In Head engines were introduced in 1966 in the Opel Rekord B and Kadett B, and soon found their way into Rekord C, Opel GT, Opel Olympia A, Manta A and Ascona A. With this new engine Opel began a new era within motorsport, which started promising with the Swede Lillebror Nasinius' championship in the Eruopean Touring Car Rally in 1966, driving a 1900 Rekord B.
The CIH were only available as 4-cylinder 1.5 - 1.7 og 1.9 litres, whereas the 6-cylinder engine were available as 2.2 litres in the Rekord C for a very short period of time, and then were available as 2.5 and 2.8 in the Commodore A, Kapitän and Admiral. When the Rekord C Sprint was marketed in 1967 a sporty version of the 19s engine featuring 2 vertical Weber DFO carburattors were put into production, and the engine was also fitted to some Kadett B's for the foreign market, USA. The engine had a poweroutput of 106 Hp. In the late 70'ies Opel started to build a 2-litre engine with larger bore, and also different versions of the 3-litre 6-cylinder engine. With the Opel Carlton the 2.2 engine were introduced, but the basis was still the old 2.0 engine. And with the Opel Omega A and Frontera the largest 4-cylinder 8-valve CIH engine at 2.4 litres were build, with a new cast engineblock and several changes compared to the 2.0 and 2.2 engineblocks.
In the late 60'ies Opel developed a crossflow cylinderhead for the Experimental Opel GT, which is the car at the back in the below picture, with the intake in the right side and the exhaust to the left side, but it was never put into production.
With the introduction of the Rekord B and the fact that Opel was given the green light by GM to particiopate in motorsports especially Swedish rallydrivers started to see the potential of the new Opel engine. And in the late 60'ies development took speed at Opel. A new crossflow cylinderhead for the 1900/2000 ccm 4-cylinder engines and the 2800/3000 ccm 6-cylinder engines, to be used in the FIA Group 2 Rally/Touring class, were put in production and sold by the Opel Sports division and Steinmetz. As a minimum 100 pieces were build to achive the homologation. The cylinderhead has an overlying camshaft with needle bearings and the second version had 2 extra boltholes for the timing chain cover due to the upgrades CIH engineblock, as well as larger ports and valves.
Later the so-called "Swedentop" was developed by Swedish rallydriers who were dissatisfied with the result that could be achieved from the standard cylinderhead and the durability of the crossflow cylinderhead. They manufactered a new cast CIH cylinderhead with larger intake ports placed higher in the cylinderhead. and considarably larger valves too. This required special intake manifolds. Later Opel copied this cylinderhead and it went into production for the Ascona/Manta B 200 Group B as well as Kadett C Group 1, and could be bought through the Opel Sports Division. Besides that camshaft, intake manifolds, and the cylinderheads were also available through Irmscher, Kissling, Mantzel and Mattig. At the same time a sporty version of the Ascona B was made, called "i2000".
An Opel 2000ccm 16-valve CIH engine were designed in 1972 as a collaboration between Steinmetz and the Opel Development Division. The engine were to be used by the Ascona A Group 4 and for the Formula 2-races in 1973. The first test runs of the F2 engine promised 317 Hpfrom the 2-litre 16-valved engine, which were more than the competitors such as BMW, Cosworth and Tecno at that time could achieve from their Formula 2 engines. Unfortunately the first test if the F2-car ended in a tragic accident were the driver died, and the homologation of the Ascona A Group 4 was delayed as Steinmetz turned insolvent, and finally the project was dropped.
A Kaiman Formula 2 2-litre 16-valved CIH engine were designed by Ludwig Apfelbeck from Kaiman, Austria, and the cylinderhead was very much different from what Opel had developed for their engine. The Apfelbeck engine was used in a March F2 driven by Dieter Quester and was said to produce more than 280 Hp.
Rallyefforts in the Opel Kadett C, Manta B, Ascona B and i400 models
In 1972 Opel experimented with building a turbocharged version of the low compression 1.9 litre export engine for the Manta A. A number of press-cars were build but the project was cancelled from various reasons and the cars were called back to the factory and assumably destroyed.
The Opel 2-litre 16-valve engine homologated for the Kadett C Group 4 was basically the same that was developed for the Ascona A Group 4, but had been developed furthermore by Schrick. As a starting point 100 cylinderheads were build for cars destined to be used in rally and these engines developed 225 Hp. Along with the rally programme Opel attempted with two cars in the German Touring Car Championship DRM with Walther Rörhl and Manfred Trint as drivers. They achieved approx. 270 Hp at 10.000 rpm. but Opel were forced to retire from both the rallies and the Touring Car Championship due to problems with the engines. In 1976 the manager of the project, Helmut Bein, were forced to resign and the project was stopped.
The Opel Ascona i400 project, and later Manta i400, was put into production in 1978 in collaboration with Cosworth. Opel had delivered cylinderheads and parts from their 2-litre 16-valve project engines and Cosworth took up the development and improvement. It is therfore not accidential that the i400 cylinderheads has 20 degrees valveangles as well as light tappets. The development of this engine was acutally started already in 1972, and Cosworth revised the pistons, conrods and crankshaft and ended up with a displacement of 2400 ccm and a poweroutput of 240 Hp. The crankshaft has 8 counterweigths and a stroke of 85mm, which makes it almost identical to some of the crankshafts from the Omega A C24NE engine. In standardspec with injection, that Opel produced for the streetversions of the Ascona/Manta i400, the engine provided 147 Hp. In Phase 1 the effect was raised to 240 Hp, Phase 2 at 261 Hp, Phase 3 at 280 Hp and Phase 4 at 300 Ho. Today effects of more than 345 Hp can be achieved with a fully optimized 2.5 litre i400 engine.
Meanwhile Irmscher started in 1978 to develop their own 16-valve 2-litres CIH engine. The first edition had chaindriven camshafts anf hydraulic tappets and as such not to be used in motorsports. The engine was displayed the first time in a Manta B CC pictured in an Irsmcher catalogue. The second edition of the engine had beltdriven camshafts which off course required some minor changes such as another timing cover. There were also procued a small number of 2.4 16-valved engines based on their second version of the 2-litre 16-valved CIH engine, and these engines were used in the Omega A Irmscher Editions.
For the Kadett C GT/E 1000-series a special 2.0EH high compression cylinderhead was developed in 1978. Besides this it is worth mentioning that the 2.2 and 2.4 cylinderheads have some differences compared to the normal 2.0 cylinderheads. The inlet and outletports sits higher in the cylinderhead which improves the flow, the combustions chamber volumes are larger and the valves are considarably larger with 40mm exhaust and 45mm intake. The valve stems on the 2.5 cylinderhead are chromed for better strength. Some of the valveheads have valveseats designed for unleaded petrol, and these cylinderheads are marked with an "Y" infront of the listed displacement and can be seen just above the spark plugs. Cylinderheads that requires leaded petrol are marked with an "X".
Bauer Motorsport built a few cylinderheads with beltdriven camshafts with parts from the BMW F2 engines designed for Group H where the engineblock must remain standard but the cylinderhead is free. Only a few were used in motorsports.
Opel also experimented with a so-called "New Generation Crossflow" cylinderhead, based on the Irmscher 16-valve cylinderhead, and were to be used at the 2.4 engines for the export market,but they were never put into production.
Kissling Motorsport built a few Opel Omega A with a 3.6 litre 24-valved engine which took part in the Veedol Endurance Championship at the Nürnburgring Nordschleife. The valvehead consisted of two cut-up i400 cylinderheads that was welded together into a 24 valve cylinderhead!
Opel also developed a version of the 3-litre 24-valve C30SE engine for motorsports, with modified crankshaft and cylinderhead, and they also experimented with a turbocharged version of the C30SE engine but it never went into production. At the same time Irmscher built a 4-litre version, the "C40SE", using a reinforced engineblock and different crankshaft. Mantzel also manufactured a 4-litre version, the "M40". When Opel for a period of time owned the Lotus company a new 3.6 litre bi-turbo engine, the "C36GET", was developed for the Lotus Omega, and it had a poweroutput of 360 Hp. The engine was a heavily modified and improved version of the C30SE. Opel also produced a sporty version of the C30SE called Evolution 500, which featured different camshafts and ECU which raised the poweroutput from 204 Hp to 230 Hp.
This article is mainly based on information found at internet forums. I would like to thank everybody who have contributed to this. If you have any comments, corrections or informations to add, feel free to contact me.