 Complete the following phrase:  In the late 1950s the Porsche 718 RSK, a two-seater sports car, was entered in Formula Two races, as rules permitted this, and lap times were promising. The 718 was first modified by moving the seat into the center of the car, and subsequently proper open wheelers were built. These 1500 cc cars enjoyed some success. The former F2 cars were moved up to Formula One in 1961, where Porsches outdated design was not competitive. For , a newly developed flat-eight powered and sleek Porsche 804 produced Porsches only win as a constructor in a championship race, claimed by Dan Gurney at the 