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The evolution of the Evolution® engine

Oxford (23 February 2014) - 1984 – the year of the Evolution® Pt1

Nineteen Eighty-Four is widely known as the great literary masterpiece by George Orwell. However, in the worldwide Harley-Davidson community, 1984 is also known as the year Harley-Davidson introduced two superb new products – one of which literally was the driving force behind the other! 1984 was the year of the Evolution® engine and it was typically introduced in a new Harley-Davidson motorcycle design and known as the FXST Softail®.

The arrival of the Evolution engine wasn’t the end result of a simple two-year development process that today’s modern manufacturing processes can achieve. In the early 1980s, computer aided design (CAD) was at its infancy and only available to wealthy industrial companies. Despite the fact Harley-Davidson was already a recognised household name, while under the control of AMF (American Machine and Foundry) the entire motorcycle industry quickly went from a period of great success in the late 1970s to one of low sales and intense competition by 1981. There was a glimmer of expectation, though, in the offices of Harley-Davidson when plans for a new engine design originally discussed in 1977 were put in place.

Plans for the new engine were going well but further development was nearly halted in 1981 when Harley-Davidson the company was bought from owner AMF by 13 investors – one of who was Willie G. Davidson, grandson of Harley-Davidson co-founder William A. Davidson.

Under new leadership, actions to prop up H-D’s success were clear and concise: new models with even greater appeal were required. Part of this action was the increase in design time of the new but still unfinished engine. It wasn’t until 1983 that the details of the ‘new’ engine finally broke cover and one year later when it appeared in five fully functional new models.

To say the Evolution engine was all-new isn’t strictly true. It was still a 45-degree V-twin motor and based on the previous and now classic ‘Shovelhead’ mill, which first saw production line light in 1966. But where the older engine had an all-iron top end, the evolution used aluminium heads and cylinders to match the alloy lower block. Obviously the cylinders featured cast iron liners for the bores but the greater use of non-iron materials made the control of engine heat a lot easier. As a better conductor of heat, aluminium certainly reduced the problems of heat build up that came with iron castings namely differing expansion rates especially between the iron cylinders and aluminium block that caused wear on gaskets and engine cylinder bolts.

Such changes along with vast improvements in the finish of machined parts made the Evolution motor ‘oil and air tight’. The addition of stronger conrods, redesigned lubrication system and electronic ignition were also part of the redesign package.

Another blessing that came with the ‘Evo’ engine was an improvement in torque and power output. New cylinder head technology, piston shape and lighter crankshaft were responsible for a healthy but claimed 15% torque and 10% power increase over the Shovelhead engine.

It didn’t take long for Harley-Davidson fans, owners and new customers to realise a miracle within Milwaukee had occurred. Pretty soon the new 1340cc (80 cubic inch) Evo engine was the one to have. By the time it too was to be phased out in the late 1990s, Harley-Davidson had produced well over a million units of the Evolution engine. And like the Shovelhead, Panhead, Knucklehead and Flathead engines before it, the Evolution engine (aka Block Head) had earned itself a well earned and respected place in Harley-Davidson’s historical timeline.

1984 – the year of the Evolution® Pt2

With the soon to be introduced Evolution® engine, Harley-Davidson knew it could also realise its plans of developing new and exciting models. Of the five new bikes to appear in 1984, one model that made use of the latest engine to the full also happened to be the basis of a successful fresh model platform that is still as successful today: Softail.

The name Softail suggests a perfectly damped and controlled chassis, which the 1984 FXST Softail had – and today’s versions still have. But to look at a Softail you wouldn’t think so because on first looks there doesn’t appear to be any form of rear suspension. Instead the rear of the Softail uses a clever under-slung (read out of sight) suspension system. This simple but effective piece of innovation allowed Harley to mimic the original one-piece hard tail frames of the first Harley-Davidson models and also favoured by custom specialists who were prevalent at the time of Softail introduction.

The use of hard tail-styling-made-saleable was nothing short of genius. Complete with the new 1340cc Evo engine, the success of Softail was virtually instant and mirrored the once again rising fortunes of the great American motorcycle manufacturer we know and love as Harley-Davidson.

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