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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 inline 4-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 being 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 cc (in the Fiat 128) to an eventual 1600 cc (in the Fiat Tipo/Tempra).

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 it's 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 throw reduces the accelerative forces on the con-rod allowing the engine to operate at significantly increased engine-speeds.

The Engine was developed for forced-induction use in the Fiat Uno Turbo Mk I and further refined for the MK II and later the Punto GT.

As with its bigger brother the famous Fiat DOHC (aka Fiat/Lancia twincam) engine, the Fiat SOHC engine was shared with the Fiat subsidiary Lancia (appearing in 1500 cc guise in the Lancia Delta/Prisma of the 1980s) as well as being used in the Fiat 128 derived Yugo.

The final incarnation of the 128 SOHC engine was modified to utilise a new 16v DOHC engine. The engine (using the designation "Torque") featured the bore-spacing, bore and stroke of the 1580 cc 159/160 series engine with a new 16v DOHC cylinder-head. To incorporate the extra oil-return-paths and symmetrical head (as opposed to the asymmetric SOHC head) the cylinder-block was slightly revised making the DOHC head non-interchangeable with the previous incarnations of the 128 engine. Development of the Torque engine took place in the US rather than Italy whilst Fiat was under the ownership of GM. The Torque engine (178.B3 - 182.A4) powered the Brava/Bravo, Marea and Multipla Fiat automobiles as well as the second-generation Lancia Delta (never sold in the UK) finally ending production in 1999.

Engine specifications

The Fiat SOHC engine was produced in a number of configurations differing in stroke and bore but maintaining a standard bore-spacing. The first generation of 128 derived engines used a stroke of 55.5 mm and a bore of 80 mm to produce a displacement of 1116 cc. The bore was increased to 86 mm (maintaining the 55.5 mm stroke) to give a displacement of 1290 cc for the X1/9. The original 1290 cc 128/X1/9 engine is the only one of the family to have used the 86 mm bore. The second generation used bores of either 80 mm or 86.4 mm with strokes of 55.5mm or 63.9 mm giving four possible engine capacities. The final generation of SOHC engines standardised on a longer 67.4 mm stroke with either an 80.5 mm or 86.4 mm bore (giving 1372 cc and 1581 cc respectively).

Applications

List of vehicles utilising variations of the Fiat SOHC engine.

Fiat

• Fiat 128: 1969-1985
• Fiat 127: 1971-1987
• Fiat Regata: 1985-1990
• Fiat Ritmo/Strada: 1978-1988
• Fiat Punto Mk I: 1993-1999
• Fiat Uno: 1983-1995
• Fiat Tipo: 1988-1995
• Fiat Tempra: 1990-1995
• Fiat X1/9: 1972-1989

Lancia

• Lancia Delta: 1979-1994
• Lancia Prisma: 1980s
• Lancia Dedra: 1990-1998

Yugo

• Yugo 45
• Yugo 55
• Yugo 60
• Yugo 65

Images

• Fiat engines