FANTASTIC FOUR 25-26, with its Thing-Hulk battle, remains the best example of Jack Kirby cutting loose with his trademark fight-kinetics. However, despite a shorter length, the first major battle between the Hulk and the Mighty Thor-- appearing in JOURNEY INTO MYSTERY #112-- is nothing to sneeze at.
Rather than coming up with a new reason for the Asgardian hero to confront the Green Goliath, Lee and Kirby choose to tell an "untold story" of a previous meeting. Thor himself narrates the story to a gaggle of young admirers, revealing that during the Avengers' sortie against the team of the Hulk and the Sub-Mariner in AVENGERS #3, Thor managed to get the Hulk alone in a room and the two of them matched muscles for roughly a minute. This, Thor tells his comics-audience (but not his listeners), is all the time the hero allows himself to defeat the Hulk, swearing not to pick up his dropped hammer until he defeats his monstrous opponent. Since in those days Thor would revert to the human Doc Blake if the hammer was out of his hands for more than 60 seconds, this sounds like a suicide impulse on Thor's part-- though it certainly fits in with his Viking macho rep.
It's a good fight, but the panels above capture a curious dichotomy in the Lee-Kirby corpus: an admiration for the brutal power of the Hulk played off against Thor's embodiment of the virtues of nobility. The THOR feature would sometimes explore these issues, resonant of class conflict, but here it's just a side-note to the Clashing of Titans.