Opel Cam-in-head engine

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Cam-in-head engine
Opel cih engine without valve cover.jpg
Production 1965 - 1998
  • Four-cylinders:
  • 1,492 cc (1.5 L)
  • 1,584 cc (1.6 L)
  • 1,698 cc (1.7 L)
  • 1,897 cc (1.9 L)
  • 1,979 cc (2.0 L)
  • 2,197 cc (2.2 L)
  • 2,410 cc (2.4 L)
  • Six-cylinders:
  • 2,239 cc (2.2 L)
  • 2,490 cc (2.5 L)
  • 2,594 cc (2.6 L)
  • 2,784 cc (2.8 L)
  • 2,968 cc (3.0 L)
  • 3,615 cc (3.6 L)
Cylinder bore
  • 82.5 mm (3.25 in)
  • 85.0 mm (3.35 in)
  • 87.0 mm (3.43 in)
  • 88.0 mm (3.46 in)
  • 88.8 mm (3.50 in)
  • 92.0 mm (3.62 in)
  • 93.0 mm (3.66 in)
  • 95.0 mm (3.74 in)
Piston stroke
  • 69.8 mm (2.75 in)
  • 77.5 mm (3.05 in)
  • 85.0 mm (3.35 in)
Cylinder block alloy Cast iron
Cylinder head alloy Cast iron
Valvetrain Cam-in-head
Cooling system Water-cooled

The Opel Cam-In-Head engine ("CIH" for short) is a series of inline engines which was built from 1965 until 1995 and was available in four- or six-cylinder configurations. Its name derives from the location of the camshaft, which was a compromise between an overhead valve and an overhead cam layout. The camshaft was mounted above the cylinder but aside the valves and actuated them through a very short tappet and a rocker arm, because it was not near enough to act directly upon the valves. The layout was an evolutionary dead-end and was not adapted for other engines. The 4-cylinder CIH was largely supplanted by the Family II unit as Opel/Vauxhall's core mid-size engine in the 1980s, with a large capacity 2.4L version of the CIH remaining in limited production until 1998 in the Omega A and latterly, the Frontera A models. The 6-cylinder versions of the CIH remained in volume production until 1995.

There was also a diesel engine using this layout, first seen in the Opel Rekord D in 1972.


The CIH is not a true overhead camshaft design, although the camshaft is mounted in the cylinder head, driven by a roller chain - rather it can be thought of as a "hybrid" between an overhead valve (OHV) and an OHC configuration. Later versions used hydraulic tappets, a design which was pioneered by Opel for mass market production. The valves were in a reverse flow layout, both mounted on the right side of the engine (when longitudinally mounted). This led to lowered fuel economy but was considerably cheaper to manufacture. The head and block are both made from cast iron. The CIH engine was oversquare, with the original three versions having a very short stroke of only 69.8 mm (2.75 in). Later engines of over 2000 cc received longer strokes, up to 77.5 mm (3.05 in) for the 2.2 and 85.0 mm (3.35 in) for the 2.4 (also used for the 3.6 litre inline-six version).

While an improvement over an OHV engine, the advantages over an OHC design were limited. The biggest one may have been cosmetic, with the lower head allowing for a correspondingly lower bonnet line. The CIH engine was also lighter (although this was negated by the use of a cast iron head) and it should require less maintenance than the more common OHC design.[1]

Four-cylinder versions[edit]

1.5 liter model[edit]

This is the first iteration seen, introduced simultaneously as the 1700 and 1900 variations. A 82.5 mm (3.25 in) bore and a 69.8 mm (2.75 in) stroke means a 1,492 cc (1.5 L) displacement. 15N and 15S (low and high octane versions, for Normal and Super) were on offer, as with most of Opel's engines of the 1960s and 1970s. Power ranged from 58 to 60 PS (43 to 44 kW) for the 15N while the rare 15S (only installed in the export only Kadett B 1.5) has 65 PS (48 kW).

This engine went on to be built by Daewoo (it had been imported by Daewoo's predecessor companies GM Korea and Saehan Motors) in South Korea beginning in around 1983. The automobile taxation system of South Korea greatly favours engines of less than 1.5 litres displacement. It was installed in the Saehan Camina, the Saehan Gemini/Daewoo Maepsy series, and in the Saehan/Daewoo Royale (until 1987). 1.9 and 2.0 liter versions were also built in Korea.


1.6 liter model[edit]

The 1,584 cc (1.6 L) version has a larger 85.0 mm (3.35 in) bore and the same 69.8 mm (2.75 in) stroke as most CIH fours. It was introduced in September 1970 with the all new Opel Manta A and then, seven weeks later, in the Opel Ascona A. The 16N uses lower octane fuel and has a lower compression ratio, while the more powerful 16S uses higher octane petrol. Power outputs were 68 and 80 PS (50 and 59 kW) at the time of introduction; the outputs were lowered after the beginning of 1975 when desmogged engines were introduced. Output was now 60 and 75 PS (44 and 55 kW) respectively. From 1975 there was also a cleaner yet A16S version with 69 PS for some markets.


1.7 liter model[edit]

As explained before, the 1698 cc version was one of the three to be introduced originally. Bore is 88.0 mm (3.46 in) bore while the stroke remains 69.8 mm (2.75 in). The 1700 was only ever available in carburetted form, for either normal or super petrol with corresponding power outputs. Power outputs are 60 and 75 PS (44 and 55 kW) for the original 17N and 17S versions. The output of the 17N increased to 66 PS (49 kW) in 1969, and then back down to the original 60 after the compression was lowered in 1975. The 17S received a new carburettor setup in 1972 (when the Rekord D was introduced) and power climbed to 83 PS (61 kW). The 17S was more popular in export markets where engine displacement was directly linked to owners' costs, countries like Italy and Greece.


1.9 liter model[edit]

A 19S engine fitted to a 1970 Opel GT

The 1897 cc version was the third version originally introduced. Bore is 93.0 mm (3.66 in) bore while the stroke remains 69.8 mm (2.75 in). The 1900 was available in carburetted or fuel injected forms, for either normal or super petrol with a variety of power outputs (the N version was a later addition). Output is 90 PS (66 kW) for the original 19S. There was also the 19HL (Hochleistung, or "high power"), introduced in 1967 for the sporty Opel Rekord Sprint and Kadett Rallye Sprint models. This version has 106 PS (78 kW), compared to 97 PS (71 kW) for the slightly more powerful 19SH (only fitted to the Rekord). The 19SH lost some power in 1975 (down to 90 PS) and the new 19N was introduced to replace the discontinued 17S; like the 17S it offered 75 PS (55 kW) but used cheaper gasoline and more relaxed driving characteristics. The 1900 is the most common version in the CIH family, available in the most versions and with the longest production time.

The 19E was the first of the CIH four-cylinders to receive fuel injection; with 105 PS (77 kW) it first appeared in the Manta GT/E in March 1974. There is also a low-powered version of the 19N (the A19N) with 69 PS (51 kW) which was mostly fitted to the Opel Rekord E, and a special low emission version for the Swedish and Swiss markets, called the S19S, which develops 88 PS (65 kW).


2.0 liter model[edit]

The 1979 cc version was based on the 1.9 litre version, with the bore expanded to 95.0 mm (3.74 in) bore while the stroke stubbornly remained 69.8 mm (2.75 in). Unlike the earlier 1.9, the 2.0 also received hydraulic tappets. Developed to counteract the diminishing outputs which resulted from stricter emissions rules, the 2.0 was available in carburetted or fuel injected forms, for either normal or super petrol with a variety of power outputs. Output of the original 20S, presented in September 1975, is 100 PS (74 kW) at 5200 - 5400 rpm. Soon there was also the fuel injected 20E version, with 110 PS (81 kW), and the slightly more powerful (115 PS) 20EH fitted to the Kadett 2.0 GT/E. This received the Bosch L-Jetronic system, until it was replaced by the updated LE-Jetronic towards the end of 1981. A 90 PS (66 kW) 20N version appeared in August 1977. There are also two special low emission versions for the Swedish and Swiss markets, called the S20S and S20E, with slightly less power than their dirtier counterparts.


2.2 liter model[edit]

The 2.2 CIH engine was fuel injected or carbureted and was produced in 1984 through 1987. It was used in Opel Rekord E, Opel Monza A2 and Opel Senator A2.

2.4 liter model[edit]

The 2.4L capacity version was the final 4-cylinder CIH engine, first used on the Omega A in the German market (the 2.0L Family II unit was the top spec 4-cylinder engine option for the Omega in most markets outside of Germany), the final application was in the Frontera SUV vehicle.


Six-cylinder versions[edit]

The modern (1968–1993) straight-6 was used in the largest Opel and Vauxhall cars. It was displaced by the Opel-designed 54° V6 in the mid 1990s.

These engines were cam in head cam chain driven, units with carburetors in the 1960s and 1970s, but was later fitted with Bosch fuel injection in the early 1980s.
A special 24v head design appeared on the Carlton/Omega and Senator in the beginning of the 1990s, this was later turbocharged by Lotus for the 1990s Lotus Omega/Carlton.


This is the rarest model of the inline-sixes, with only 2239 cc. It shares its dimensions with the smallest, 1.5 liter "four", meaning a 82.5 mm (3.25 in) bore and the regular 69.8 mm (2.75 in) stroke. It was first seen in December 1966. With 95 PS (70 kW) it had only marginally more power than the 1900S, at a substantial weight and cost penalty. It was removed from the Rekord C subsequent to the introduction of the six-cylinder Commodore line in February 1967, and was discontinued entirely towards the end of 1968, when the 1969 models were introduced.



The modern Opel straight-six line began in 1968 with the 2.5 L (2490 cc) 25S unit used in the Opel Commodore. Still a 12-valve engine, it had a very oversquare 87.0 mm (3.4 in) bore and 69.8 mm (2.7 in) stroke. 9.5:1 compression and a single carburettor produced 117 PS (115 hp/86 kW) and 174 N·m (128 lb·ft), while 9.0:1 compression and dual carbs produced 132 PS (130 hp/97 kW) and 186 N·m (137 lb·ft).



At the introduction of the 24v DOHC engine in Senator/Carlton/Omega, the 2.5 increased volume to 2.6 litres and with a reworked cylinder head (still with twelve valves) and RAM Induction it now produced 150 PS (110 kW; 148 hp). This engine was also fitted to southeast Asian export market versions of the Holden VP, VR, and VS Commodores between circa 1992 and 1997. These cars were usually labelled "Opel Calais".


The 2.8 was introduced in the first Commodore model. The carburated version can also be found in the Monza and Senator, while the second Commodore was also available with a fuel-injected version producing 150 PS (110 kW; 148 hp).


The 3.0 L (2969 cc) version was introduced in 1977 alongside the fuel-injected 2.5.
The carburated version had 150 hp (112 kW), while in the more popular fuel injected version, the 3.0 produced 180 PS (178 hp/132 kW) and 248 N·m (183 lb·ft) in the Opel Monza GSE and Opel Senator 3.0E, as well as their Vauxhall badged equivalents (the Royale and later the Senator) Bore was increased to 95.0 mm (3.7 in), but the stroke remained at a very short 69.8 mm (2.7 in).

The 1986 Opel Omega 3000 / Vauxhall Carlton GSi introduced the latest version of the 3.0. The injected engine produced 180 PS (177 hp/132 kW) and 240 N·m (177 lb·ft). Amongst the changes were larger valves and a switch in engine management to Bosch Motronic. This engine later found its way into the Senator and Omega 3.0i.

In 1989, a DOHC 24-valve version with a variable length intake manifold was introduced, with power increasing to 204 PS (150 kW) and 270 N⋅m (200 lbf⋅ft).

The Omega Evo had a special Irmscher version of the 24-valve engine with an uprated head and forged internals producing 230 PS (169 kW; 227 hp).


Irmscher made a 3.6i 12v engine and fitted this 36E coded engine into the Monza E and Monza GSE models. In the UK some of these engines that were originally designated for an Opel Monza found their way into Vauxhall Senator B's instead.

Later on in 1987, they put newer, more environmentally friendly versions of this engine in special Irmscher versions of the Omega A/Mk3 Carlton and Senator B models. These later units (200 PS or 147 kW or 197 hp) output engines had 36NE/C36NE/C36NEI engine codes and were less powerful than the first 207 bhp (154 kW) engines that were used to power the earlier Opel Monzas. There were also 24-valve versions of the 3.6 developed.


4.0i 24v DOHC versions were made both by Irmscher and Mantzel who are well known tuning companies in Germany. The 3983cc Irmscher engine had a C40SE code and was the only one out of these two engines that used a specially cast engine block as part of this increased capacity engine conversion. Mantzel's 4032cc engine used an M4024V code number and a modified standard 30NE/C30NE/C30LE/C30SE coded Opel engine blocks for its four-litre conversions.
The Irmscher version was an option in the Opel Omega Evolution 500 models, producing 272 PS (200 kW; 268 hp)

Lotus 3.6 twin turbo[edit]

The Lotus Omega/Carlton introduced a stroked to 85 mm (3.35 in) version of the engine with same bore of 95 mm (3.74 in), now displacing 3,615 cc (3.6 L; 220.6 cu in). Lotus used twin Garrett AiResearch T25 turbochargers and an air-to-water intercooler along with a compression ratio of 8.2:1 and custom fuel injection. The turbos were arranged in parallel, each fed by and feeding three cylinders. The company reportedly experimented with a variety of forced induction schemes, including paired supercharging and turbocharging and sequential turbos, before settling on two small turbos for quick spool-up. The Lotus engine produced 382 PS (377 bhp; 281 kW) @ 5200 rpm and 568 N⋅m (419 lb⋅ft) @ 4200 rpm.


The CIH engine had a long competition career, in both four- and six-cylinder forms. It won the 1966 European Rally Championship, with Swedish driver Lillebror Nasenius at the wheel of an Opel Rekord B. Competitions departments quickly changed the less than competitive layout of the head, with crossflow versions developed by a number of tuners such as Steinmetz, Mantzel, and Irmscher.[2] Later models received four-valve heads, a layout also used by Opel themselves for the Manta 400 and the later 24-valve sixes in the Omega A and Senator B. The most powerful iteration was the 380 PS (279 kW; 375 hp) twin-turbo 3.6 litre C36GET as used in the Opel Lotus Omega/Lotus Carlton.

A four-litre version (C40SE) was also developed by Irmscher, and installed in the Opel Omega A and Senator B. These engines have a bore and stroke of 98 mm (3.9 in) and 88 mm (3.5 in) respectively, for an overall displacement of 3,983 cc (243 cu in). Power is 272 PS (200 kW; 268 hp).


  1. ^ Matt (2013-05-03). "Technical Curiosities: Opel's Cam-In-Head Engine". Spannerhead. Retrieved 2013-12-07. 
  2. ^ "The history of the development of the Opel CIH engine, 1966-1993". Customs and Classics. Archived from the original on 2013-05-29. Retrieved 2013-12-07.