The engines used in the Honda Civic, Accord and Prelude are water cooled, overhead cam, transversely mounted, inline four cylinder powerplants. They can be divided into two different engine families; CVCC and non-CVCC.
The non-CVCC engines have been offered in two different displacements; 1170cc (1973 only), and 1237cc (1974-79). These engines are somewhat unusual in that both the engine and the cylinder head are aluminum. The cylinder head is a crossflow design. The block uses sleeved cylinder liners and a main bearing girdle to add rigidity to the block. The engine uses five main bearings.
The CVCC (Compound Vortex Controlled Combustion) engine is unique in that its cylinder head is equipped with three valves per cylinder, instead of the usual two. Besides the intake and exhaust valve, each cylinder has an auxiliary intake valve which is much smaller than the regular intake valve. This auxiliary intake valve has its own separate precombustion chamber (adjacent to the main chamber with a crossover passage), its own intake manifold passages and carburetor circuit.
Briefly, what happens is this; at the beginning of the intake stroke, a small but very rich mixture is introduced into the precombustion chamber, while next door in the main combustion chamber, a large but very lean mixture makes its debut. At the end of the compression stroke, ignition occurs. The spark plug, located in the precombustion chamber, easily ignites the rich auxiliary mixture and this ignition spreads out into the main combustion chamber, where the large lean mixture is ignited. This two-stage combustion process allows the engine to operate efficiently with a much leaner overall air/fuel ratio. So, whereas the 1975 and later non-CVCC engines require a belt driven air injection system to control pollutants, the CVCC accomplishes this internally and gets better gas mileage.
On the 1983 models, Honda decided to improve engine breathing by replacing the single large main intake valve with a pair of smaller ones. This allows a much greater total intake valve area than a single valve and it also permits intake valve timing to be staggered slightly. This gave Honda engineers a unique opportunity to design air swirl into the combustion process. Such swirl not only tends to reduce engine knock but improves combustion speed and therefore engine efficiency, especially at low speeds. These engines retain the auxiliary intake valve on the exhaust side of the head.