7 Technical Facts About The Harley Davidson Shovelhead
The Harley Davidson Shovelhead engine, first introduced in 1966, was a groundbreaking V-twin that improved both power and performance. Here are seven key technical facts about this iconic engine.
1. Introduction of the Shovelhead Engine
In 1966, Harley Davidson launched the Shovelhead engine, featuring a 74-cu.-in V-twin engine and an OHV Big Twin chassis. This new engine was designed to offer more power and improved performance, leading to its status as one of Harley's longest-running models. The Shovelhead remained in production until 1985.
2. Power Increase and Design Improvements
The Shovelhead engine featured a 26% increase in sales, reaching 36,310 units. The 1966 model had aluminum versions of the Sportster iron heads, earning it the nickname ‘Power Pac’ for its 10% power increase. This boost in performance was achieved with straighter intake ports and longer fore-and-aft fins.
3. Improved Combustion Chamber Design
The Shovelhead's shallow combustion chambers were designed to minimize surface area, which reduced heat dissipation. Compared to earlier models with 90-degree valve chambers, this design improved cooling and performance at higher compression rates.
4. Changes to Alternators and Gearboxes
Between 1966 and 1968, Shovelhead models did not feature alternators, instead using generators. These models were equipped with a four-speed gearbox and an all-chain drive. The Iron Sportster heads also featured long exhaust ports, with varying port angles between the front and rear cylinders.
5. Valve Sizes and the Impact of Wet Sumping
The Shovelhead engine featured intake valves sized at 1.94 inches and exhaust valves at 1.75 inches. However, the engine was prone to ‘wet sumping,’ where oil from moving parts would settle in the crankcase instead of being returned to the oil tank. This issue could slow the engine down, particularly on long rides.
