Passing the break at 300 metres, the long striding Cuban was a couple of steps ahead of the noticeably smaller American Rick Wohlhuter.
Sriram Singh came from more than 10 metres back at the break to sprint past Juantorena and the rest of the field, to take the lead just after the bell.
Wohlhuter stuck less than a mere step behind Juantorena all the way through the final turn as Ivo van Damme, Willi Wülbeck and future champion Steve Ovett jockeyed for position.
Despite the erratic pace, Singh's time in 7th place stood as the Asian record until it was broken by Lee Jin-il in 1994.
None of the 1972 finalists returned; the Kenyan boycott kept Munich bronze medalist and would-be favorite Mike Boit out.
The favorites among the athletes who did appear were Alberto Juantorena of Cuba, Rick Wohlhuter of the United States, and Ivo van Damme of Belgium.