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 (1984-1999/2000)
Displacing the same 80 cubic-inches (1340cc), the Big-Twin Evolution motor was more powerful and ran cooler and smoother than the Shovelhead.
In 1999, it was replaced by the Twin Cam 88 in Touring and Dyna models, and in 2000 in Softail models.
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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. The Twin Cam 95 (1550cc) was introduced with the Screamin' Eagle (CVO) models and ran until the TC88 was discontinued after 2006. In 2006, the TC96 was introduced, displacing 96.7ci or 1584cc. These were followed by 103- and 110 cubic-inch versions.
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Tri Glide Models
The first Tri Glide was introduced for the 2009 model year (Tri Glide Ultra Classic). It was Harley's first factory-produced three-wheeled motorcycle since the Servi-Car.
A second model, called the Street Glide Trike, was offered for the 2010 model year and discontinued after 2011.
From 2009 through 2013, Tri Glides were powered by the 103 Twin Cam.
A new model called the Freewheeler was introduced in 2015.
From 2014 through 2016, Tri Glides were powered by the High Output 103 Twin Cam.
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Milwaukee Eight (2017-present)
It's still a 45-degree V-Twin, but the Milwaukee Eight engine differs from all previous Harley Big Twins in many ways.
The motor has a single camshaft with four valves per cylinder, and is air and oil-cooled. Engine displacements produced are 107, 114, 117, and 121.
For 2017–2018, Tri Glides were powered by the 107 Milwaukee-Eight.
From 2019 to present, Tri Glides are powered by the 114 Milwaukee-Eight.
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