C40SE

Cam-in-head engine
Overview
Production	1965 - 1998
Combustion chamber
Configuration	I4 I6
Displacement	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
Combustion
Cooling system	Water-cooled
Chronology
Predecessor	Vauxhall Slant-4 engine Opel Straight-6 engine (I6)
Successor	Family 1 engine (1.5-1.7 L) Family II engine (1.8-2.4 L) GM 54-Degree V6 engine (I6)

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, as 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).

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Wikipedia