Fiat SOHC

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Designed by Aurelio Lampredi, the Fiat SOHC engine first appeared in the front-wheel drive (FWD) Fiat 128 of 1969. The in-line four-cylinder engine comprised an iron block with an aluminium cylinder-head containing a single over-head camshaft operating directly on both the inlet and exhaust valves in a reverse-flow cylinder-head configuration. The camshaft was driven by a belt rather than chain. The engine remained in production until the mid 1990s and grew in capacity over the years from 1100&nbsp;cc (in the Fiat 128) to an eventual 1600&nbsp;cc (in the Fiat Tipo/Tempra). Also appearing in 1969, the Fiat V6 130 engine 2866&nbsp;cc, although no reverse-flow cylinder-head, is directly related to the 128 SOHC engine, with a 1.20 upscale in bore and stroke.

Design and production

The engine was designed as a transverse mounted FWD-only power-plant being the first engine/gearbox combination to exhibit the now standard transverse engine-next-to-gearbox layout with unequal length driveshafts (the Mini had its gearbox in the sump of the engine). The one exception to the engines FWD-only design is its revolutionary use as a mid-engine drive-train in the Fiat X1/9.

A prominent feature of the Fiat SOHC engine its massively over-square proportions. 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...
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