MoneyINC Logo
Years of

The Story of the Harley Davidson Knucklehead

Harley Davidson Knucklehead

Have you ever heard of the Harley-Davidson Knucklehead? If you are a motorcycle aficionado, there is absolutely no doubt that you know exactly what it is. As a matter of fact, you might have not only heard of it, but perhaps you even own one yourself. Assuming that you are either new to motorcycle riding or you're just exploring a topic that you're mildly interested in, yet haven't decided to give your full attention to, the Harley-Davidson Knucklehead is not a particular motorcycle, per se. In reality, it actually refers to a particular engine that is installed on some of their motorcycles. In some cases, you'll hear someone refer to one of their bikes as a Knucklehead, meaning that it has that particular engine. Conversely, you might hear someone refer to another Harley-Davidson motorcycle as a Panhead. Again, this is referring to the type of engine that has been installed. Here is some information on the history of the Harley-Davidson Knucklehead. Along the way, you'll have the chance to enjoy some interesting tidbits and facts about it that will probably only serve to make you want to know more.

The Name Isn’t an Official One

One of the more interesting things to note is that the Knucklehead is not necessarily an official term that was coined by the company itself. Instead, it's a term that has become increasingly popular over time, something that's almost used as a nickname for this particular style of engine. If you're wondering where the nickname came from, it's largely because of the way the engine looks once it's been installed on a Harley-Davidson motorcycle. It's rather distinctive because the rocker boxes have a very distinct shape. At some point in time, someone referred to it as a Knucklehead and the name stuck. It's not really all that uncommon for die-hard Harley-Davidson fans to create nicknames for different motorcycles that have been produced by the company. Sometimes the nickname refers directly to the motorcycle in question and at other times, like this one, the nickname refers instead to the engine that is used. In this particular case, the Knucklehead engine has become almost as popular as Harley-Davidson itself. That is precisely why it has become popular enough to receive a nickname in the first place. As it turns out, the engine itself has quite the storied history all on its own.

Power and Performance Rolled Into One

What makes the Knucklehead engine so special? It marks only the third main type of engine that was ever used by the motorcycle company, designed to replace the Flathead engine and introduced in 1936. The engine is an overhead valve V-Twin with two valves per cylinder that is pushrod activated. As you might already know, it is a 2-cylinder engine set at 45 degrees. When it was introduced in 1936, it replaced the VL model and was designed specifically to be the company's best engine, installed only on their most high-end motorcycles. For the next several years, it would essentially reign supreme, being used almost exclusively on all of the company's best bikes.

The Emergence of the Knucklehead Engine

As previously mentioned, the Knucklehead engine became the predominant engine installed on Harley-Davidson motorcycles during the late 1930s and throughout most of the 1940s. In fact, it wasn't replaced until 1948 when the Panhead engine came along. For years and years, it was known by an entirely different nickname, one coined by Harley-Davidson themselves. At the time, it was called the OHV. Even in official Harley-Davidson literature that comes from this time period, this particular engine is referred to as the OHV. There is no point in any of this literature where the engine is referred to as a Knucklehead. In fact, that particular nickname wouldn't exist throughout the entire duration of the engine’s production. It would be several years before it would be referred to as the Knucklehead, a nickname which didn't come along until the 1960s.

A New Nickname

It's interesting to note that it would be almost 25 years after the engine was initially introduced before it would be handed the nickname that virtually every motorcycle rider knows it by today, but that is exactly what happened. As it turns out, there was a big Chopper culture throughout California in the 1960s. Somewhere along the way, a person referred to this particular engine as a Knucklehead, largely because the valve covers on it very clearly resemble the knuckles on a person's hand whenever a fist is made. It didn't take long for this nickname to begin circulating. In almost no time at all, this particular engine was almost universally known as the Knucklehead. The nickname may have started in California, but it spread from state to state with the same speed as the company’s fastest motorcycle running flat out. From that point forward, virtually every Harley-Davidson motorcycle that incorporated this particular engine also became known as a Harley-Davidson Knucklehead.

It Only Takes a Single Look

One of the most distinctive features of Harley-Davidson motorcycles in general is that they tend to change the shape of their valve covers in such a manner that someone who knows a thing or two about their history (and about motorcycles) can simply take a look at those valve covers and tell what type of engine has been installed. More often than not, they can also tell you what types of motorcycles the engine was used on, the years that that particular engine was manufactured, how it works and how much horsepower it is capable of providing. This certainly became the case with the Knucklehead engine, as it has become something that virtually every Harley-Davidson fan is familiar with. Considering the fact that the engine itself hasn't been used since the 1940s, a great deal can be said about the history of both the engine itself and Harley-Davidson motorcycles in a more general sense.

A Cultural Icon

After all, there are plenty of motorcycle manufacturers out there who don't have this type of cult following. In fact, many people would be hard-pressed to simply look at some other manufacturer's engine and know exactly what type of engine has been installed at first glance. This is something that is largely unique to Harley-Davidson. In part, it is because of the distinctive valve covers, as previously mentioned. However, it also has something to do with the fact that people who ride Harley-Davidsons are a special group of individuals in the best way possible. They are extremely passionate about the motorcycles they ride and they tend to know every square inch of their bike from one end to the other. The truth is, a seasoned Harley-Davidson rider can usually tell you more about a Harley that isn't even their own than most motorcycle “experts” who are talking about some other manufacturer’s product.

Stamping Their Place in History

It isn't just their unique appearance that made the Harley-Davidson Knucklehead something that was highly sought after, both when it was in production and even still today. At the time that it was introduced, the bike had far more power than its predecessor and it was capable of turning heads, even the heads of those who traditionally weren't all that interested in motorcycles. As a matter of fact, the bike with the unique appearance that was absolutely unmistakable was also capable of setting a number of records, often during a time when the country was looking for some type of diversion because things weren't exactly running along smoothly. When you consider the time that this particular engine was popular, it's easy to see how many other things were going on not only in the United States, but also throughout the world. You have the end of the depression and the duration of World War II, just to name a couple of things. Things were difficult and people were looking for something that would give them hope, often something that provided a unique distraction from the difficulties associated with war, famine and a sluggish economy. The Harley-Davidson Knucklehead was able to provide that.

Setting Records

In 1937, Joe Petrali set a record at Daytona by running a specially-designed Harley-Davidson Knucklehead for a mile, something that had become the true test of virtually all motorcycles at the time. His top speed was just over 136 mph, setting a record and astonishing those who were fortunate enough to witness the event. At the time, no one could have even dreamed that a motorcycle would be capable of going that fast. Granted, he was essentially riding on behalf of the company. As such, they had taken everything off of the bike that wasn't absolutely necessary for its operation. It was definitely not the same Harley-Davidson that someone who purchased a bike from a dealership would have, meaning that it was considerably faster than most of the street-legal motorcycles being produced by the company. Nevertheless, it was capable of achieving a record that lifted the spirits of an entire nation and provided a much-needed distraction, even if for only a few moments.

More Records to Come

That same year, Harley-Davidson set out to show the public that it was possible to set records with the same street legal, base model that could be purchased directly from a dealer. As such, they set up a project where someone would ride one of their base models that was capable of producing about 37 horsepower for 24 hours, with the only stops being those made to fuel up. The idea was to showcase how reliable the Harley-Davidson was as well as to showcase its overall speed and performance. In that 24 hour time period, the motorcycle covered a distance of 1,825 miles. Just as the company had hoped, it set a new endurance record. This provided even more proof to the general public that the company was capable of producing something that was not only fast and flashy, but also reliable. From there, the Harley-Davidson Knucklehead was stamped into the minds and hearts of people all over the United States. Even though it was replaced with the Panhead engine roughly 10 years later (as previously discussed), the Knucklehead has gone down in history as one of the most storied Harley-Davidson engines that has ever existed.

Still a Classic

Today, the Harley-Davidson Knucklehead is considered by many to be one of the most coveted bikes the manufacturer has ever made. As such, a lot of people dream about owning one for themselves. The problem is that the engine hasn't been produced since the late 1940s, meaning that it's not always easy to get your hands on one. It's even more difficult to find a Harley-Davidson motorcycle that incorporates the Knucklehead engine which is still in good enough shape to be restored without doing a complete rebuild of virtually every component from one end to the other. That said, it isn't impossible. As a result, many people who are hardcore collectors set their sights on this particular goal and they won't quit until they have one of their own sitting in their garage. The question is, how much is it likely to cost you if you dream of owning a Harley-Davidson Knucklehead yourself?

The Cost of Greatness

In 2014, there was an auction that occurred in Australia that involved more than 20 different types of automobiles and motorcycles totaling more than $2 million. Just one of those examples was a Harley-Davidson Knucklehead. It's worth noting that this particular bike had been completely restored and had never been used since that restoration was completed. At the time, it commanded a purchase price of $65,000. This was believed to have been the most expensive sale price for any Harley-Davidson Knucklehead in history. As you can see, there is a great deal of history behind the Harley-Davidson Knucklehead. If you want to own one for yourself, it's not likely to be cheap. In fact, it's far more likely that it will cost you a great deal of money, especially if you're lucky enough to find one that is fully restored. Nevertheless, it might very well be worth it because you will most definitely be owning a piece of history that relatively few people can be a part of.

Benjamin Smith

Written by Benjamin Smith

Benjamin Smith is one of the managing editors of Moneyinc. Ben's been focusing on the auto and motorcycle sector since 2005. He's written over 1000 articles in the space and continues to learn about it each day. His favorite car is "any Bugatti" and he's a die hard Harley Davidson fan.

Read more posts by Benjamin Smith

Related Articles

Stay ahead of the curve with our most recent guides and articles on , freshly curated by our diligent editorial team for your immediate perusal.
As featured on:

Wealth Insight!
Subscribe to our Exclusive Newsletter

Dive into the world of wealth and extravagance with Money Inc! Discover stock tips, businesses, luxury items, and travel experiences curated for the affluent observer.
linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram