On August 20, 1978, the Champion Spark Plug 400 was held at Michigan International Speedway as the 20th race of the 30-race 1978 NASCAR Winston Cup Series season, drawing an estimated attendance of 50,000 for a 36-car field contesting 200 laps on the 2-mile track.
David Pearson captured the pole in the #21 Purolator Mercury for the Wood Brothers. Pearson scored the victory with a last-lap pass, finishing 0.32 seconds ahead of Cale Yarborough. Darrell Waltrip finished third, followed by Dave Marcis and Bobby Allison. Pearson led 56 laps and averaged 129.566 mph in a race that featured 34 lead changes and was slowed by seven cautions for 35 laps.
