A sports car specialist who won the 1970 International Championship of Makes and the Interserie Championships in 1971, 1972 and 1973. He had a brief foray into F1 with a Surtees TS16 but soon returned to the more familiar world of sports cars.
Kinnunen raced successfully for a number of seasons in his native Finland with Volvos, Porsches and an F3 Titan.
In 1969 he won the Nordic Challenge Cup driving a Porsche 908 and as a result was asked by John Wyer to join his Gulf-Porsche in the 1970 International Championship of Makes. He won his debut race, the Daytona 24 Hours, driving with Pedro Rodriguez and Brian Redman. He teamed up with Rodriguez for the rest of the season, winning the Championship. They won four races that year; Daytona, Brands Hatch, Monza and Watkins Glen. Leo also set a new lap record at the Targa Florio of 33'36" for the 71.9 kilometer long road circuit.
He also raced in the Interserie Championship and the European Sportscar Championship driving a 2-litre works Abarth 2000SP. He came 2nd at Mugello and 3rd at the Nurburgring. With twelve points he came 11th in the Championship.
In 1971 he drove the AAW Racing Team's Porsche 917 Spyder in the Interserie Championships. At the Norisring Leo and the second Ferrari driver Herbert Müller retired from the race after the tragic accident of Pedro Rodriguez in the Ferrari 512M. Leo went on to win the Championship for Porsche.
As hard working as ever he also entered a private Porsche 911S with Björn Waldegaard in an ICM round at Nürburgring coming 16th and he teamed up with Rolf Stommelen in an Autodelta Alfa Romeo T33/3 again at the Targa Florio, only for the German to crash out on the first lap.
In 1972 he drove exclusively for AAW Racing in the Interserie Championship, totally dominating the series in his Porsche 917/10, winning six of the nine rounds at Silverstone, Hockenheim (twice), Norisring, Keimola and the Nurburgring. He won the Championship with points being transferred straight into cash, Leo earned 135.000 Swiss francs (now about 300.000 US dollars).
For the 1973 Leo Kinnunen was joined by fellow Fin Hannu Sirviö. Leo won four of the seven rounds in the AAW Racing entered Porsche 917/10 , winning the Interserie Championship for the third time in a row. He also entered the Targa Florio again driving a Martini Racing Porsche Carrera 911 with Claude Haldi they finished 3rd.
In 1974 Leo got his shot at Formula One. AAW Racing entered a Surtees TS16 Cosworth but it was under powered and handled poorly. This coupled with the teams inability to secure top quality tires led to Leo returning to Interserie after Monza.
AAW Racing quit F1 at the end of the year. Leo won his first race back in sports cars was with the Martini Racing Team Porsche 917/30 at Hockenheim.
He continued racing for Martini in 1975 with a Porsche 908 turbo driving with Herbert Müller. They retired in Monza and Spa but were 7th at Enna, 3rd at the Nürburgring and 9th at the Österreichring.
For 1976, Kinnunen drove a Porsche 934 Turbo with Evon Egertz in the World Championship of Makes. He came 4th at Dijon, 3rd at Mugello and Silverstone, and 2nd at Watkins Glen. In the other championship, the World Sportscar Championship, he drove a Porsche 908 with Evon Egertz but they retired from Monza and Dijon with mechanical problems.
In 1977 he competed in one race at the Nürburgring round of the WCM. He failed to finish the race retiring with engine problems in a Josef Brambring Porsche 935 shared with Jürgen Neuhaus and Albrecht Krebs.
Leo Kinnunen left the international motor racing scene after 1977 and started his own business in Finland.