Also, Tofaş has adapted 128 engines into its Fiat 131 based longitudinally-mounted, front-engine, rear-wheel-drive layout platform.

This over-square design allows large (within the constrains of a reverse-flow configuration) valve sizes relative to engine capacity.

A secondary benefit is the short crank throw, which reduces the accelerative forces on the con-rod allowing the engine to operate at significantly increased engine-speeds.

The Fiat SOHC engine was produced in a number of configurations differing in stroke and bore, but maintaining a standard bore-spacing.

Multi-point fuel injection (MPI) was introduced late in the 138 series to help meet lowered emission requirements in the US.

The plenum was slightly redesigned to a more angular "box" shape for the 3rd generation engines and was again pressurised for the Uno and Punto GT Turbo models.

For the 3rd generation engines, the down-draft carburettor was replaced with a Single-point injection system (SPI) in the base-level models.

The Fiat Tipo/Tempra/Punto 1.6 8v (75-90hp) is commonly used as a base because it's easily accessible and is de-tuned from factory (especially the 75hp versions), leaving tuners with a lot of headroom for horsepower increase.

Common modifications are: swapping to a better carburetor, using a higher overlap/lift camshaft, bigger intake/exhaust valves, lowering the head to increase compression and a tuned 4-2-1 exhaust manifold.

Traditionally both down-draft (DCNF & IDF) and side-draft (DCOE) twin-choke carburettors have been used to extract more power from the 128 derived engines.

Low-cost DIY Fuel Injection (FI) controllers (such as MegaSquirt) have made it easier to alter the characteristics of the early MPI systems and release similar potential as the DCNF/DCOE carburettors.

It is possible to "chip" the later digital MPI systems, though aftermarket FI controllers again give greater flexibility.

To remedy this (in addition to the introduction of MPI) camshafts for emission-restricted markets featured asthmatic low-lift, low-duration, low-overlap profiles totally unsuited to the nature of the 128 engine.