Less then two months later he pounded out a ten round verdict over future title challenger Manuel Ramos. The following year he whipped tough trial horse George “Scrapiron” Johnson. In 1966 he fought a No Decision bout with Amos “Big Train” Lincoln and he lost a decision to highly regarded Zora Folley.The year 1967 saw Henry establish himself as a force in the heavyweight division by winning on points over Bill McMurray, Steve Grant on two occasions, Fred Lewis, Eddie Machen and Roger Rischer.
Henry opened 1968 by defeating the clever Leotis Martin. This led Henry into a major bout against come backing ex-heavyweight king Sonny Liston. This was Sonny’s first major step on his comeback trail and he passed with flying colors. Sonny pummeled a game but overmatched Clark in scoring a seventh round stoppage.
The year 1969 had mixed results. Henry drew with Brian London and kayoed Bob Stallings. He then lost on points to “Florida” Al Jones and Jeff “Candy Slim” Merritt. In 1970 his best win was a points call over Jimmy “The King” Fletcher. In 1972 Henry won and lost to Jack “The Giant” O’Halloran. He was then stopped in nine rounds by an up and coming Ken Norton on the Muhammad Ali-Bob Foster under card.
Henry came back to win three bouts in 1973 and then on March 4th 1974 in a rematch, Henry blew out the now ranked Jeff Merritt in one round. Henry quickly followed with a decision win over faded ex-contender Mac Foster. Henry remained unbeaten through four more fights. It was then matched with the dangerous Earnie Shavers in Paris, France. Try as he might for the KO, Shavers was unable to stop the wily Clark and had to settle for a hard earned points win over Henry. They met again six months later on the under card of Ali-Norton III. This time Henry was overwhelmed by the murderous punching Shavers in two rounds. Henry attempted to bounce back four months later but was defeated over ten by Howard “Kayo” Smith. Henry did not fight again for over two and a half years. When he did return he was defeated in ten rounds by fringe contender Bernardo Mercado.