Fiat - Engines 2
https://www.youtube.com/watch?v=OYtY8BveGOY
This time, you have a choice. You can watch all four parts of the video above, the other three are linked below, and/or read our summary text, which provides a comprehensive description of
the engine and its
origin.
It's an engine that originated from a collaboration between Fiat and OSCA. This company was founded by the Maserati brothers in 1947. This became necessary after the original company,
along with the rights
to the name and ten years of operation, was sold to the industrialist Adolfo Orsi in 1937.
The ten years were over, and the brothers were free. They now called themselves Officine Specializzate Costruzione Automobili. They wanted to compete in the 1,110cc class
with a vehicle. The result was a four-cylinder engine with a respectable 40 kW (55 hp) at 6,000 rpm for the post-war era. From 1948, the displacement was 1,342 cc, and from 1953, 1,453 and 1,491 cc,
respectively.
The latter is also available in the Fiat 1500 S Coupé and Cabriolet. Here, it produces 59 kW (80 hp). Just like the Lampredi engine presented in Fiat engines 1, it has a light-alloy cylinder head
with two overhead camshafts, but differs significantly in details. In total, there were just over 3,000 Fiat vehicles with this engine.
It came from a very early era. The timing belt hadn't been invented yet. It was common practice to drive the camshaft(s) with timing chains. This one used double ones, which, however, didn't
extend all the way from the crankshaft to the top, but only to an intermediate shaft. Only from there did another chain continue all the way to the camshafts.
One advantage of this design would have been smaller gears at the driven end, thus reducing the height of the motor, but the OSCA motor apparently didn't take advantage of this. A major
disadvantage compared to the timing belt was, of course, that chains can only be operated in an oil-tight environment, while timing belts only require a plastic cover, and sometimes not even
that.
However, unlike the Lampredi engine, the OSCA engine does not have to take an OHV four-cylinder into consideration, so the block was narrower. The fuel pump and distributor were driven by the
aforementioned intermediate shaft within the connection from the crankshaft to the camshafts. The engine also didn't have an oil filter.
Spin filters were also common in much more mildly tuned engines. They were located at the front end of the crankshaft behind a cover. The oil flow was routed so that it arrived here from the inside of the
crankshaft and released its unwanted ingredients to the outside through its rotational speed. An inspection then involved scraping these out from behind the cover.
This was supposed to happen from time to time behind the very shallow oil pan, but this was probably a rather sloppy job. Presumably, they were afraid of not being able to seal it again, because the oil level
was clearly higher than the pan. However, the cylinder head was a single piece with two covers, unlike the Lampredi engine.
In the civilian version, the expensive two flat-draft dual carburetors and thus their synchronization were omitted. A disadvantage, besides the lower power with a downdraft register rarburettor was the required
height, including the air filter, which necessitated an additional bulge in the hood.
The V-shaped valve positions resulting from the position of the two camshafts were very beneficial for the power output, even forcing a certain degree of flattening on the respective pistons. However, their age
was more evident in the additional oil control rings located at the bottom of the piston skirt.
Part 2:
https://www.youtube.com/watch?v=sy9mU17iGQs
Part 3:
https://www.youtube.com/watch?v=beLEKbu4c4Q
Part 4:
https://www.youtube.com/watch?v=0ms4SE8UMpY
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