If we were to say the name “Robert Glenn Johnson Jr” not many people, besides hardcore NASCAR fans, would know who we are talking about. However, mention the name Junior Johnson and “Mystery Motor” and nearly every NASCAR fan knows what we’re talking about. If you haven’t figured it out, Robert Glen Johnson Jr and Junior Johnson are the same person.
The Mystery Motor refers to Junior Johnson’s most famous car, which was a 1963 Chevy Impala SS with an extremely rare Mk II engine. This engine was a very limited production model that was wedged between the Mk I 438/409 engine and Mk IV 427 engine. This engine only saw roughly 50 total units produced, though some claim there were only 18 ever produced, making it one of the rarest GM engines ever built.
Shortly after these engines went out to various Chevrolet drivers, Chevy pulled the plug on its race sponsorship and the owners of the cars were stuck with modifying and fitting the engines themselves. Junior Johnson’s Mk II 427 wound up being the most powerful built at the time and resulted in a total of seven wins, nine pole positions, 13 top-5 finishes, and 14 top-10 finishes in just 33 races in the 1963 season. Its overall power and rarity earned it the name “Mystery Motor.”
Following the 1963 season, Chevy had began production of the Mk IV 427, rendering the Mystery Motor ineligible for NASCAR competition and reducing Johnson’s win total to less than half the following year.
If you have ever wanted to own a piece of automotive and NASCAR history, this is your chance, as RK Motors Charlotte has put Johnson’s 1963 Impala SS up for sale, Mystery Motor and all.
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