One of Germany’s most famous men was a man named Otto von Bismarck and his favourite saying was “Blood and Iron” which has led many to wonder if he was a motorcyclist. By angling the valves and designing the air flow so that it would maintain velocity throughout the engine’s cycle smaller valves set at reduced included angles optimised the air flow and “hogging out” the ports would actually reduce power because the dimensions of the system were designed as an efficient whole. In addition to these changes were the design work done on the air flow through the engine by specialists including Jerry Branch and Kenny Augustine. These tight clearances were built to ensure good heat transfer away from the pistons and into the cylinders and their cooling fins.
Piston clearance was 0.0014” and under sustained full throttle use this could drop as low as a scant 0.0004” and the Evolution engine would happily keep going. The top piston ring was chrome plated and barrel faced, the second ring had a two degree taper face, and the oil scraper was a three piece one. Pistons were Mahle, made in Germany, which had a twelve percent silicone content to reduce and stabilise expansion. The cylinders and cylinder heads were made of aluminium both to vastly improve cooling and to ensure the problems inherent with an alloy head expanding at a different rate to an iron cylinder were solved. The Evolution engines had the metallurgy sorted out, the designs refined, and were able to be built to far finer tolerances than had previously been possible. The Evolution engines not only carried forward Bill Harley’s original ideas but they also solved the problems that had beset the earlier Harley-Davidson engines, problems caused by heat – cooling, gasket sealing, and oil leaks. So between them these two Evolution engines carried forward the original design concepts of Harley-Davidson founder Bill Harley and they’re a fitting legacy to him. The Evolution appeared in 1984 in two versions the smaller Sportster Evolution (which appeared in 1986) made in 883cc and 1,200cc versions carried forward the original four camshaft design first seen on the Harley-Davidson Flathead engine of 1929, whilst the larger 1340cc Evolution Big Twin engine carried forward the same bottom end and single camshaft of the Knucklehead engine of 1936. 1984 was the year Harley-Davidson introduced what many regard as their greatest engine, and for a true blue motorcycle enthusiast who wants to be able to strip his bike down to the last nut and bolt and to be able to fix it himself/herself it is possibly the greatest Harley-Davidson engine, period. Thankfully 1984 was a great year for Harley-Davidson and not at all like the “1984” of British writer George Orwell’s novel.