In September of 1967, The Italian government green-lighted Alfa Romeo's project for its new compact family car, to be built in a brand-new factory near Naples, whose construction started on the 29th of April 1968.
Every nut and bolt in the Alfasud was new, designed by under the direction of German engineer Rudolf Hruska.
The flat-four engine configuration was chosen to lower the center of gravity and the bonnet line of the car, thus improving handling and aerodynamic performance.
Although it was designed and tested as a 1500cc engine, the Alfa Romeo boxer debuted in 1972 as 1.2 liters, single-carburetor engine, to place the Alfasud at a comfortable distance from the Giulia in the Alfa range.
Contrary to most boxer engines, the Alfa Romeo flat-four engine block was a single cast-iron piece, open on the underside to allow the fitment of the crankshaft. Once closed, the engine block then was a very solid unit, leaving plenty of potential for higher-powered derivatives. The two cylinder heads were cast in aluminum, and each had one camshaft, driven by its own individual timing belt.
Chapter One - Carbureted Boxers 1972-92
The Alfasud Ti, launched in 1973, was the first sporting derivative of the Alfasud range. The first significant evolutionary step for the boxer came in 1976, under the bonnet of the pretty Alfasud Sprint coupé.
That first 1.3 liters engine was to be shortlived though, superseded in 1978 with a new version that shared its stroke with the 1.5 liters engine that debuted that same year. Both power units would gain their typical two double-barrel carburetors in 1979 and be carried over mostly unchanged from the Alfasud to the 33, in 1983.
The end of Alfasud production did not spell the end of the entry-level 1.2 liters boxer though, which went on powering the base version of the Arna until the end of that model's run, in 1987.
By the mid-80s, 1.5 liters were no longer enough to compete at the upper end of the European C-Segment, so the sportiest of the 33, the Quadrifoglio Verde, received a thumping 118HP 1.7 liters engine. This version of the 33 can be considered a swansong for the lusty, throaty carbureted boxers, as these were gradually replaced by fuel-injected units.
Chapter Two - Fuel-Injected Boxers 1988-97
The first boxer to be offered with electronic fuel injection was a slightly tamer version of the new 1.7 liters engine, available from 1988 on the successful 33 range. From 1993 all the boxers were fuel-injected: these may not sound quite as good as before, but look nicer due to those lovely aluminum intake manifolds, at least in my opinion!
By 1990, the Alfa Romeo boxer engine and the 33 reached their evolutionary peak, with the introduction of the range-topping 1.7 16 valves. The cylinder heads were redesigned entirely, with two camshafts per bank: the engine, also thanks to the higher compression ratio, produced a healthy 132HP at a heady 6500Rpm.
Not that it mattered too much, as the boxer's days were numbered due to the need for better economies of scale within the Fiat Group. Its life was extended for a few more years, until 1997, only because not enough Fiat-derived inline-four engines could be produced in time for 1994, the year the 33's replacement was launched.
Therefore, the development of the boxers stopped altogether, with the smaller versions retaining the older cylinder head design right until the end.