V-Twin Engine History: Head-to-Head With the Panhead, Knucklehead & Shovelhead
The Knucklehead V-twin is the Motor Company’s first overhead-valve twin
Harley-Davidson replaced its Flathead mill with the then-new Knucklehead V-twin engine in 1936. It was a formative motor for the MoCo, introducing the brand’s first overhead-valve (OHV) engine in a production motorcycle.
With a two-cylinder, 45-degree V-twin construction, the Knucklehead has much of the DNA you’d expect to see in the marque’s latest big twin, the Milwaukee-Eight (M8) engine. However, being an early OHV attempt by Harley-Davidson, the Knucklehead had its shortcomings.
For starters, some of the early OHV mills had lubrication issues and developed leaks. Also, early iterations of the Knucklehead engine had valve springs prone to premature wear and breaking.
So, what kind of name is “Knucklehead?” Well, the V-twin engine takes its name from the characteristic rocker covers. Fans thought the rocker covers looked a pit like a fist with bulbous knuckles, hence “Knucklehead.”
Panhead: Replacement for the Knucklehead
After World War II, Harley-Davidson replaced the Knucklehead with the Panhead V-twin engine. Gone were the cast-iron cylinder heads. In their place, the two-valve-per-cylinder Panhead packed aircraft-inspired aluminum heads. Boom. The Panhead was much better suited to high heat than its predecessor.
Like the Knucklehead, the Panhead gets its unique name from its shape. Harley-Davidson used single-piece valve covers to top the twin. Polished up, the saucer tops resembled pans. And the “Panhead” was born. The Panhead engine filled Harley-Davidson frames from 1948 to 1965 when the Shovelhead twin replaced it.
Not unlike the brand’s first OHV engine, the Panhead had its growing pains. Literally. The soft aluminum in the Panhead’s cylinder heads would expand and contract more rapidly than the iron heads of its predecessor. As a result, the Panhead would experience valve issues.
The Shovelhead dug out a path for the Evolution, Twin-Cam, and M8 V-twin engines of the future
It’s 1966. California elects Ronald Reagan as the state’s governor. John Lennon apologizes for the “more popular than Jesus” comment. And Harley-Davidson rolls out the Shovelhead twin, a successor to the Panhead. Rather than a pan-ish appearance, the Shovelhead’s rockers resembled a shovel, hence the name.
The new OHV was an improvement over the previous two mills. For starters, the Shovelhead worked in improved cylinder heads, better porting, and stronger internals. Better yet, the Shovelhead was available with both an 80-cubic-inch and 74-cubic-inch displacement.
Fortunately for the Motor Company, the Shovelhead was a popular mill, and sales reflected that fact. However, that didn’t stop the Shovelhead from a replacement in the Evolution twin in 1984.
Photos: Unsplash, Getty Images
You must be logged in to post a comment.