The cars that the youngsters (in Sweden called "raggare") drive in the movie are from the late 50s and early 60s. In the 60s the "raggare" drove cars from the 40s.
The valve who connects the compressed air to the paintbrush in the movie didn't come to use until the early 1980s.
Near the end of the movie after finishing the race there is a sign that says "Anbud" (offer in English) at one of the houses. This sign is for folk racing which didn't come to Sweden until 1981.