One of the greatest engineering feats in motorcycling history has to be the Harley Davidson Panhead engine. Named for the distinct pan-like rocker covers, this engine first came into being in 1948, having been inspired by the previous generation of Harley Knucklehead engines that were used during the war.
Its designers kept the knucklehead’s transmission and bottom-end crank. To improving cooling, they switched out the iron cylinders and heads with new aluminium alloys. The heads were modified to take on an inverted pan design that would better contain the head-leak problem that had plagued patrol bikes using the knucklehead engine. They also installed a new oil pump that would provide better lubrication and flow to sustain faster engine speeds.
This initial design was however not without problems. The use of new alloys also meant the metal would expand when heated. The valves now activated by new pushrods were also at increased risk of valve lash, due to the increased distance from the cylinder base. The potential for burnout was tempered with hydraulic tappets, but still left the valves vulnerable to wear and tear due to the temperature fluctuations and lack of lubrication from being at the top of the engine.
A few years later the problem was resolved by shifting the tappets into the oil of the crankcase, creating an FL high compression engine. This successful edit would persist for many years, with just a few alterations along the way to accommodate the cruising needs of police bikes. These engines came with smaller cams and carburettors that made it more comfortable to ride at slower speeds for extended periods.
The mid-60s saw a transition from the kickstart to electric starters. Not a highly popular modification amongst hardcore Harley Davidson enthusiasts, it resulted in a new nickname for the final Panhead-styled engines, the Electra-Glide. Following disappointing sales of these bikes, the Panhead era came to an end.
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