The in-line four-cylinder engine comprised an iron block and an aluminium cylinder head with pushrod actuated valves.

The 100-series engine has a three main bearing crankshaft, a cast iron block and an aluminium cylinder head with an integrated intake manifold.

There were 2 overhead valves per cylinder, actuated by an OHV valvetrain.

Early versions were fed by a carburettor, but single point fuel injection with catalyst would appear in the early '90s to fulfill anti-pollution laws, along with electronic Distributorless Ignition System.

List of vehicles utilising variations of the Fiat 100-series engine.