The Australian 1½ Litre Formula was a motor racing category which was current in Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

 from 1964 to 1968. The formula specified racing cars

Racing Cars

Racing Cars are a Welsh pop band, formed in the Rhondda Valley, Wales in 1973.-Career:They were signed to one of the biggest British record labels of the time, Chrysalis Records. Racing Cars's debut album yielded their only hit single with "They Shoot Horses, Don't They?"...

 with four cylinder unsupercharged engines using commercially available fuel and limited to 1500cc capacity. It occupied the second tier in Australian formula car racing, below the Australian National Formula

Australian National Formula

The Australian National Formula was an Australian motor racing category which was introduced by the Confederation of Australian Motor Sport in 1964 and remained current until the end of 1969...

 (which specified a 2500cc engine capacity limit) and above Australian Formula 2 (1100cc) and Australian Formula 3

Australian Formula 3

The Kumho Tyres Australian Formula 3 Championship is a motor racing championship for FIA Formula Three racing cars and is now the official Australian Drivers' Championship. Growing out of Australian Formula 2 racing into a series for the first time in 1999, it has grown into the premier Australian...

 (1000cc).

Drivers of Australian 1½ Litre Formula cars contested their own national title, the Australian 1½ Litre Championship

Australian 1½ Litre Championship

The Australian 1½ Litre Championship was a CAMS sanctioned national motor racing title contested annually from 1964 to 1968. It was open to drivers of cars complying with the Australian 1½ Litre Formula which specified open wheel racing cars fitted with unsupercharged engines using commercially...

 and were also eligible to compete alongside Australian National Formula drivers in the Australian Drivers' Championship

Australian Drivers' Championship

The Australian Drivers' Championship is a motor racing championship which has been contested annually since 1957 by drivers of cars complying with Australia's premier open-wheeler racing category as determined by the Confederation of Australian Motor Sport. Since 2005 this category has been Formula...

, the Australian Grand Prix

Australian Grand Prix

The Australian Grand Prix is a motor race held annually and is held to be the pinnacle of motor racing in Australia. The Grand Prix is the oldest surviving motor racing competition held in Australia having been held 76 times since it was first run at Phillip Island in 1928. Since 1985 the race has...

  and the Tasman Cup Series. The Australian 1½ Litre Formula was discontinued as at the end of 1968 and the engine capacity limit for Australian Formula 2 was raised from 1100cc to 1600cc for 1969.