Retrotechtacular: Constructing A Car Engine

Oxford is a city world-famous for its university, and is a must-see stop on the itinerary of many a tourist to the United Kingdom. It features mediaeval architecture, unspoilt meadows, two idylic rivers, and a car plant. That’s the part the guide books don’t tell you, if you drive a BMW Mini there is every chance that it was built in a shiny new factory on the outskirts of the historic tourist destination.

The origins of the Mini factory lie over the road on a site that now houses a science park but was once the location of the Morris Motors plant, at one time Britain’s largest carmaker. In the 1930s they featured in a British Pathé documentary film which we’ve placed below the break, part of a series on industry in which the production of an internal combustion engine was examined in great detail. The music and narration is charmingly of its time, but the film itself is not only a fascinating look inside a factory of over eight decades ago, but also an insight into engine manufacture that remains relevant today even if the engine itself bears little resemblance to the lump in your motor today.

Morris produced a range of run-of-the-mill saloon cars in this period, and their typical power unit was one of the four-cylinder engines from the film. It’s a sidevalve design with a three-bearing crank, and it lacks innovations such as bore liners. The metallurgy and lubrication in these engines was not to the same standard as an engine of today, so a prewar Morris owner would not have expected to see the same longevity you’d expect from your daily.

The film starts with forgings, and the manufacture of crankshafts, gears, and connecting rods from forging, machining, and grinding, to the drilling of oilways. It is at this point we see the first of a series of specialised automatic machine tools and grinders, showing us the scale of the Morris operation at the time. We move on to castings, and see a freshly-cast engine block being ground, milled, drilled, and tapped. The sheer numbers of drills and taps in a single machine are impressive, though if you’ve ever broken a tap in an engine block you’ll probably be wincing a little. The die-cast pistons are next to be machined, and their oulways are reilled with yet another specialist multi-way drilling machine.

A number of components such as camshafts and gudgeon pins are turned from bar stock, their faces being case-hardened where necessary. The engine may have significantly changed over the years, but as anyone who’s had a modified camshaft built will tell you this is a recognisable process in the manufacture of their modern equivalents. Surprisingly we also see small components such as screws being manufactured, where today a specialist screw supplier would be called upon to bring them in ready-made, in the 1930s Morris saw fit to manufacture their own.

The film concludes with a montage of the engine assembly line, during which we see the archaic coil-spring clutch, flat sidevalve head, and camshaft drive. There is an interesting continuity error here, in that some of the engines being assembled are Morris’s six-cylinder unit rather than the 4-cylinder one we saw earlier, but we’ll forgive the producers that one.

It is probable that a few of the processes in the 1930s engine factory would be recognisable in its modern equivalent, but it is also obvious that this is an archaic factory by today’s standards. Surprising is the high level of machine tool automation at a time when numerical control was probably not even a gleam in [Joseph Gerber]’s eye, but it is worth remembering that as the largest carmaker in the country the Morris factory would have represented the absolute cutting edge of automotive manufacture. You’re looking at the 1930s Tesla Gigafactory.

We mentioned earlier that the factory in this film is now no longer in existence. Morris had by the late 1960s become a component of the nationalised British Leyland group of carmakers as the British government tried to arrest the decline in the industry. By the 1970s the name appeared only on the Morris Marina, a car with an outdated 1950s design in a 1970s body that has become the butt of countless jokes about the Leyland cars but which your scribe can tell you from personal experience was excellent for drifting on wet roundabouts when her parents had one as the family car in the 1980s. In the early 1990s the original works was closed and demolished, with production of cars then badged as Rovers moving across the road to the site of Morris’s pressed steel works. A controversial ownership change left that operation in the hands of BMW, and it remains the base of their British operation. Meanwhile Morris cars are a regular sight on the classic car circuit, and there are still a few old guys driving Minors and Marinas round Oxford that they bought before retirement from the plant.