The original design of the cam-in-head engine was done by General Motors in Detroit, Michigan.

Although the camshaft is in the cylinder head, the CIH is not a true overhead camshaft design.
Rather it can be thought of as a cam-in-block engine with a greatly shortened valve drivetrain.
The camshaft is driven by a roller chain.
While the earliest engines used mechanical lifters, later versions used hydraulic tappets, which Opel pioneered for mass market production.
The cylinder head is a non-crossflow layout.
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 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 mm (3.35 in) for the 2.4 (also used for the 3.6 litre inline-six version).

While an improvement over a cam-in-block engine, the advantages over an OHC design were limited.
For one, the lower head allowed for a correspondingly lower bonnet line.
The CIH engine was also lighter (negated somewhat by the use of a cast iron head) and was expected to require less maintenance than an OHC design.

Opel developed their own crossflow head for the CIH block, and tested it in the experimental GT-2 of 1975 with the intent of installing it in the production model.
This engine reached only limited production as a 4 cylinder as the 2.0EH in the Kadett GT/E.. It did see mass production in 6 cylinder form as the 3.0 24V in the Opel Senator B.
The original design of the cam-in-head engine was done by General Motors in Detroit, Michigan.
Although the camshaft is in the cylinder head, the CIH is not a true overhead camshaft design. Rather it can be thought of as a cam-in-block engine with a greatly shortened valve drivetrain. The camshaft is driven by a roller chain. While the earliest engines used mechanical lifters, later versions used hydraulic tappets, which Opel pioneered for mass market production. The cylinder head is a non-crossflow layout. 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 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 mm (3.35 in) for the 2.4 (also used for the 3.6 litre inline-six version).
While an improvement over a cam-in-block engine, the advantages over an OHC design were limited. For one, the lower head allowed for a correspondingly lower bonnet line. The CIH engine was also lighter (negated somewhat by the use of a cast iron head) and was expected to require less maintenance than an OHC design.
Opel developed their own crossflow head for the CIH block, and tested it in the experimental GT-2 of 1975 with the intent of installing it in the production model. This engine reached only limited production as a 4 cylinder as the 2.0EH in the Kadett GT/E.. It did see mass production in 6 cylinder form as the 3.0 24V in the Opel Senator B.
Opel cam-in-head engine