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.
Knucklehead models include E (standard), EL ("sport"), F (74ci), and FL ("deluxe" 74).
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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.
Panhead models include EL (61ci), FL (74ci), Hydra-Glide, and Duo-Glide. The final year Pan (1965) was the first Electra Glide, which introduced electric start and a 12-volt electrical system.
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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.
Shovelhead models include FLH Electra Glide, FLT Tour Glide, FX Super Glide, FXS Low Rider, FXB Sturgis, and FXWG Wide Glide.
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Blockhead/Evo (1984-1999/2000)
Displacing the same 80 cubic-inches (1340cc) as the late Shovelhead, the Big-Twin Evolution motor ran cooler and was more powerful. Both the heads and cylinders were made from aluminum to reduce weight.
To many, Evo rocker boxes looked like squared-off Panhead rocker boxes, prompting the early nickname "blockhead", which really never caught on.
Evo models include Touring, FXR, and Dyna, and the all-new FXST Softail.
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Road King Handlebar Adjustment
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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.
Although the Twin Cam 88 was seen on 1999 Dyna and Touring models, it was not offered on Softails until 2000. The Softail family received the "88b" motor, which featured two chain-driven balance shafts.
On Dyna models, the engine was rubber-mounted, which helped minimize vibration to the frame and rider.
NOTE: It is possible to mount a standard Twin-Cam motor to a pre-2000 Softail through aftermarket adapters.
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 for 2007 models, displacing 96.7ci or 1584cc. These were followed by 103- and 110 cubic-inch versions.
Along with the popular Dyna, Touring, and Softail models, the Street Glide "factory custom" debuted as a 2006 model.
Pictured: Cross Bones Softail Springer, produced from 2008 through 2011.
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Three-Wheeled Harleys
The Tri Glide was offered for the 2009 model year as the 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.
From 2014 through 2016, Tri Glides were powered by the High Output 103 Twin Cam. The Freewheeler trike was introduced in 2015.
With frame-mounted sharknose fairings, the Road Glide 3 (trikes on left in picture) debuted in 2023 and are powered by the Milwaukee-Eight engine.
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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 is air and oil-cooled, and has a single camshaft with four valves per cylinder. Engine displacements are 107, 114, 117, and 121.
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