This young man had a vintage automobile (for the 60s) and was taking his innocent young date out for a drive, something that seemed popular back in that era. It's also damned naughty because those couples often stopped for a roll in the grass.
Today's 60s vintage porn movie is just that. The only way they could get any privacy was to go out in the country and this hardcore pair was desperate for some bang! They get it, and we get some rollicking good porn from the heyday of porn, the 1960s.