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Evolution engines were built from 1984 till 1999.They can be identified by the blocky rocker boxes, which earned them the nickname Blockhead.These were 1340cc/80ci engines that replaced the Shovelhead. Both the heads and cylinders are made from aluminum which helps with cooling and is lighter than its cast iron predecessors.Yet another improvement was that the heads were redesigned to allow for a higher compression ratio.These new engines were designed on a computer which resulted in a smoother,quieter,more powerful and reliable ride. Not every Big Twin in 1984 had an Evo engine Shovels were still being made at this time.Some of the first production still had a 4 speed transmission with solid mounts.Although isolated mounts and a 5 speed were offered in the early eighties.All who stuck with the Shovelhead did not have this option they were still solid mount with a 4 speed.