At the Academy of Fine Arts (AVU), Prague, Valenta made the acquaintance of Jan Koblasa, Aleš Veselý, Zbyšek Sion, Zdeněk Beran, Antonín Málek, and other artists from the circle of future private exhibitions entitled Confrontations (1960)
He became friends with Mikuláš Medek and Vladimír Boudník. In 1960 he participated in the organisation of the unofficial studio exhibitions Contractions I and II, which introduced the issue of Art Informel to the Czech environment. He participated at both Confrontations. The first Confrontation was actually held in his studio in Libeň, Prague, on 16 March 1960. Valenta was also a member of the putative though never officially established group of abstractionists “Confrontations 1961”.
In 1963 he exhibited a selection of abstract drawings at the Mánes Fine Artists’ Club, and a year later participates at the exhibition “D” (Nová síň Prague, 1964), which introduced personalities of Czech contemporary abstract art, with an emphasis on authenticity. The first of Valenta’s large, independent retrospectives entitled Pictures from 1959 - 1965 was organised in 1965 by the City of Brno House of Arts at the Building of the Lords of Kunštát.
The following year an exhibition of his latest work was held in the Young Artists’ Gallery at Mánes, Prague. From the middle of the sixties onwards Valenta’s works were regularly shown at important foreign exhibitions of Czech contemporary art. He is one of five young painters from Eastern Europe represented by the Lambert Gallery on the occasion of the 4th Young Artists’ Biennale in Paris.
He first joined the Federation of Fine Artists in 1967. He participated at the exhibition Fantasy Aspects of Contemporary Czech Art (OVG Jihava, Špála Gallery Prague 1967), re-evoking the lines of imaginative creation.
From the end of 1967 he participated on designing the refurbishment of the Catholic chapel in Stáj u Jihlavy (the architect of which was M. Hrubý), where along with the colour white and a simply contoured symbolism he applied the meditative effects of light. The project remains unfinished as a consequence of the political changes in 1968.
Shortly after the occupation he left for Germany via Vienna. From 1968 to 1969 he lived with the Berlin gallerist Jarry Kilian in Hof Donau u Eutin in Northern Germany, where he had acceptable conditions for his work. In 1970 he moved to Plön and acquired experience with the art of ironwork. The Emil Nolde Foundation in Seebüll awards him a prestigious stipendium in 1971 which Valenta used to systematically create numbers sequences of simple, mainly white symbolic pictures and drawings.
In 1972 he moved to Brühl and then to Kolín nad Rýnem, where he settled permanently. In 1973 he took up a post at the Kolín municipal authorities, where he worked on publicity graphics and compilation of the land use plan. In the middle of the seventies he brought his painting to a close and became actively involved in photography. He was a keen traveller. At the end of the eighties he died of lung cancer.