A leading figure in Canadian national racing in the late 1960s, Wietzes made his Grand Prix debut at the wheel of a rented Lotus at the first World Championship Canadian Grand Prix in 1967. He made little impact but went on to a more successful career in the SCCA Continental Championship (which became the Formula 5000 series). He finished fourth in the series in a McLaren M10B in 1970 and repeated the result the following year in an M18. In 1972 he raced a Lola T300 and won at Donnybrook and finished fifth in the championship while in 1973 he was sixth overall in a T330. He drove a rented Brabham in the 1974 Canadian GP but continued to specialize in F5000, finishing fourth in the US series in a Lola T332 that year and fifth in a Lola T400M in 1975.