Harley Big-Twins Through The Years
Article by Mark Trotta
2026 marks 90 years of the overhead valve Big-Twin Harley.
Before that, Big-Twin Flatheads led the line-up (1930 to 1935).
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Knucklehead (1936-1947)
Originally known as the "61 Overhead", the Knucklehead displaced 61 cubic-inches from 1936 through 1940. With consumers requesting more power, a 74 cubic-inch version was optional from 1941 to 1947.
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Panhead (1948-1965)
The Panhead motor was also offered in 61 or 74ci displacements, with the smaller engine discontinued after 1952.
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Shovelhead (1966-1983)
Replacing the Panhead in 1966, the 74ci Shovelhead motor was designed to run on premium leaded fuel. When the 80ci version came out in 1980, it was designed for premium unleaded.
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Blockhead (1984-1999)
Displacing the same 80 cubic-inches (1340cc) as the Shovelhead, the Big-Twin Evolution motor was more powerful and ran cooler and smoother.
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Twin Cam (1999-2017)
Named for it's pair of chain-driven camshafts, early model Twin Cams displaced 88 cubic-inches, followed by 103- and 110 cubic-inch versions.
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Milwaukee Eight (2017-present)
Although it's still a 45-degree V-Twin, the Milwaukee Eight engine differs from all previous Harley Big Twins in many ways.
It is air and oil-cooled, and has a single camshaft with four valves per cylinder.
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