Summary

• Harley-Davidson’s Big Twins have developed through the years, from the highly effective F-Head to the long-lasting Knucklehead, Panhead, and Shovelhead engines.
• Each technology of Big Twins has introduced enhancements in energy, reliability, and know-how, with larger pistons and extra superior engineering.
• The newest Milwaukee-Eight and Revolution MAX engines supply essentially the most energy and superior options but, operating cooler and smoother than ever earlier than.

For over 120 years, Harley-Davidson has been one of many best bike producers to ever exist. Since its inception in 1903, the model has continued to design and produce a few of the largest industry-changing bikes to hit the highway, and encourage increasingly new riders. An enormous a part of Harley-Davidson’s mass-appeal has been its fixed growth of the Big Twins, which have been a few of the torquiest, horsepower-heavy engines to ever be the beating coronary heart of a Harley-Davidson bike.

Throughout the a long time, Harley’s Big Twins have passed by a large number of names: Knucklehead, Panhead, Shovelhead, Evolution, and many others. In its earlier type, the Harley Big Twin was a two-cylinder piston engine, with every piston related to a single crankshaft by way of their connecting rods. Because it took on a V-shaped formation, its pistons would not fireplace at even intervals. Instead, the pistons would fireplace on each different rotation of the crankshaft, producing a smoother sound.

More latest variations just like the Twin Cam and Milwaukee-Eight, include larger pistons, in addition to extra complicated engineering. But they’re nonetheless primarily based on their earliest predecessor. With every Big Twin changing into extra highly effective and technologically superior as every new technology comes alongside, they proceed to be a few of the strongest, and most dependable drive trains available on the market.

The following info was sourced from Harley-Davidson, Ultimate Motorcycling, Your Moto Geek, Low Brow Customs, Motorcycle Classics, Power Sport Guide, and Thunderbike

F-Head, Flathead, and Knucklehead

1911 – 1973

If we’re going to undergo the historical past of Harley-Davidson’s Big Twin engines, we’ve to start out on the very starting. From 1911 to 1929, the IOE (consumption/inlet over exhaust) F-Head motor was the unique Big Twin to be put in on the early Harleys that will vary from 61 to 74 cubic inches. These days, that does not sound like a lot. But within the early 1900s, the F-Head may as effectively have been a rocket ship.

• Pro: Classic classic Harley-Davidson
• Pro: Historical significance
• Con: Low energy by as we speak’s requirements
• Con: 3-speed gear field

From 1929, the Flathead was the next Big Twin Harley-Davidson developed following the success of the F-Head. It obtained its nickname “Flathead” due to its flat-topped, vented cylinder heads, and debuted with a forty five cubic inch engine. It wasn’t till 1930 when a 74 cubic inch Big Twin arrived with the intention to sustain with its most important competitor, the 74 cubic inch Indian Chief.

In 1937, Harley launched the U collection of the Flatheads, which took the place of the V collection engines. Both the U and UL Harley-Davidsons had been geared up with the 74 cubic inch engines, whereas the UH and ULH fashions obtained the upgraded 80 cubic inch variations. The 74 cubic inch U and UL fashions remained in manufacturing till 1948, and the 80 cubic inch variations noticed a shorter shelf life after being discontinued in 1941. What is most attention-grabbing in regards to the Flathead is that the 74 cubic inch engine remained in manufacturing up till 1973, outliving many different Big Twin engines on this checklist.

• Pro: Improved cooling over the F-Head
• Pro: Increased air circulation
• Con: Air circulation wanted to make a 90-degree flip internally
• Con: Could not journey for lengthy distances

Another Big Twin that was produced alongside the Flathead from 1936 to 1947 was the famous Knucklehead, which was obtainable in 61 cubic inches and 74 cubic inches. One key distinction between the 2 was that the Knucklehead was the primary Harley engine to characteristic overhead valves and an efficient oil circulation system to maintain the interior workings effectively lubricated. As for a way the Knucklehead (aka the “EL model”) obtained the nickname “Knucklehead” was as a result of the silhouette of its rocker bins form of resembled the knuckles of a fist.

• Pro: Stiffer valve springs
• Pro: Flywheel diameter elevated to eight,500 inches
• Con: Leaky rocker bins
• Con: Gaskets broaden and contract when heads warmth up and funky down

Panhead and Shovelhead

1948 – 1984

From 1948 to 1965, the subsequent Harley-Davidson Big Twin to take up the mantle was the iconic Panhead, which was obtainable in each 61 cubic inch and 74 cubic inch fashions. How this engine obtained its title was resulting from its signature rocker covers that resembled a pair of cast-iron pan skillets, solely they had been product of aluminum and featured hydraulic valve lifters. By 1965, the Electra Glide of that mannequin yr launched the usage of electrical starters for what can be the ultimate rendition of the Panhead. Despite being in manufacturing for lower than twenty years, the Panhead stays one of the crucial beloved and revered Big Twins in Harley-Davidson’s historical past.

• Pro: Tougher and extra dependable than its predecessors
• Pro: Much louder sound
• Con: Frequent oil leaks
• Con: Clunky gear field

From 1966 to 1984, the subsequent Big Twin to comply with within the Panhead’s footsteps was the Shovelhead. Just like its predecessors, the Shovelhead obtained its nickname primarily based on the actual form of its rocker covers. Only with this engine, they appeared to appear to be a pair of small shovels, with the push rod tubes resembling the handles. It was additionally this time in Harley-Davidson’s historical past when the bottom stage of energy output was raised to be obtainable in each 74 and 80 cubic inches.

Aside from holding loyal prospects completely happy, the corporate wanted to extend the facility of its Big Twins to maintain up with the rise of the general weight of its bikes being produced within the manufacturing facility. It was additionally throughout this time when Harley-Davidson was picked up from AMF, which aimed to streamline manufacturing via excessive portions of bikes, fairly than high-quality.

• Pro: More highly effective than the Panhead
• Pro: Louder than the Panhead
• Con: Poor gas economic system
• Con: Potential rougher rides

Evolution, Twin Cam, and Revolution

1984 – 2016

From 1984 to 1999, Harley-Davidson was going via a really massive transformation after 13 buyers (together with Willie G. Davidson) re-acquired the corporate again from AMF. As it was being lapped by Japanese rivals like Honda and Yamaha within the engine division, the corporate needed to dig itself out of a rut, each financially and public fame.

This was the spark that result in the mighty 80 cubic inch Evolution engine, which served as proof that Harley-Davidson might evolve with a extra highly effective, technically superior Big Twin, identical to different main bike producers. As a outcome, the Evolution (aka “Evo”) can be a way more sturdy rendition of the Shovelhead. It ran cooler, smoother, and would be capable to run far for much longer. It additionally regained the respect and adoration of devoted Harley-Davidson riders.

• Pro: Technologically extra superior than the Shovelhead
• Pro: Resurrected Harley-Davidson out of its financial droop
• Con: Needed frequent repairs
• Con: Unfixable crankshaft seal leakage

From 1999 to 2016, Harley-Davidson launched a more moderen Big Twin that many fashionable Harley riders are extra acquainted with. That is, after all, the Twin Cam. Available in 88, 95, 96, 103, and 110 cubic inch fashions, the Twin Cams obtained its title not via the form of its rocker heads, however via the pair of chain-driven cams that it was powered by.

More highly effective and torque-heavy than the Evo, Twin Cams had been additionally the primary Big Twins to be obtainable in each carburetor and gas injected iterations. It additionally surpassed the Evo when it comes to oil circulation due to its improved inside oil pump, holding it far more lubricated, in addition to having the ability to generate higher quantities of compression.

• Pro: Increase in horsepower, torque, and displacement
• Pro: Nearly 20 years of higher reliability
• Con: Early Twin Cam 88’s skilled points with oil leakage
• Con: Models just like the 2004 Dyna Superglide and the 2005 Softail Deluxe handled cam chain defects

Another specific Big Twin that stands out within the early 2000s is the Revolution. Unlike different Harley V-twins, the Revolution was liquid-cooled and set at a 60-degree configuration, fairly than the usual air & oil-cooled 45-degree V-twins. It was additionally developed in partnership with the highest engineering minds at Porsche.

The outcome was one of many mightiest Big Twins of its time, and was featured solely within the high-performance cruiser, the V-Rod as both a 69 cubic inch or 76 cubic inch engine. This energy output made this specific Harley-Davidson a power to be reckoned with when its most important rivals had been common home road bikes.

• Pro: High-powered cruiser that was in direct competitors with sport bikes
• Pro: Co-designed with Porsche
• Con: Not for newbie riders
• Con: Low floor clearance

Milwaukee-Eight and Revolution MAX

2017 – Present

In 2017, Harley-Davidson kicked issues up a notch with their new line of Milwaukee-Eight engines. Starting at 107 and 114 cubic inches, the Milwaukee-Eight obtained its title by the eight valves featured in each cylinders. It additionally goes by the nickname “Wafflehead” due to its valve covers showing like waffle irons, nevertheless it hasn’t fairly caught on along with your common Harley rider.

These Big Twins would go on to utterly change the Twin Cams in each the softail cruisers and touring models, and stay in manufacturing as we speak. As of now, the sizes of the Milwaukee-Eights have elevated to 117 and 121 cubic inches, and improve kits can be found with max outputs of 135 cubic inches.

Aside from producing extra horsepower and torque than any of its predecessors, the Milwaukee-Eight can also be extra technologically superior due to its use of two spark plugs per cylinder, eight valves, and a higher capability for air circulation. The result’s an engine that runs cooler and smoother than some other Big Twin ever made.

• Pro: Much much less warmth
• Pro: Much extra energy
• Con: Cold begin points
• Con: Vibrations

In 2021, Harley-Davidson unveiled a brand new successor to the liquid-cooled Revolution engine discovered within the V-Rod. The 1250 Revolution Max made its first look in Harley’s groundbreaking off-road Adventure bike, the Pan America, and later within the revamped Sportster line with the Sportster S. This engine was in a position to ship huge quantities of torque (94 lb-ft) in addition to horsepower (150 hp). It additionally confirmed itself to be an ideal instance of Harley-Davidson having its finger on the heart beat of the market, which has many youthful riders wanting sooner, extra athletic bikes.

The outcome confirmed itself to be a extremely superior marvel of engineering, that includes a highly-efficient oiling system, solid aluminum cylinder heads, high-compression 13:1 pistons produced from cast aluminum, a main and secondary balancer to maintain the engine operating clean, and extra. In addition, the Revolution Max doubles as a part of the bike’s chassis, bolted instantly onto the entrance, mid, and rear body items.

• Pro: Lighter weight
• Pro: Extremely free-revving powerplant
• Con: Definitely NOT for newbie riders
• Con: Very mild pull on the clutch

Sources: Harley-Davidson, Ultimate Motorcycling, Your Moto Geek, Low Brow Customs, Motorcycle Classics, Power Sport Guide, and Thunderbike