Like Frank says, the propane torch isn’t gonna cut it….Trying to rock the bolt using only the propane will probably snap it off….You will need to find a bigger acetylene torch for this job…
One more idea…..Are all the head bolts out except for the one frozen one? If so,, try tapping on the head (with a heavy plastic mallet) in the direction of loosening the bolt. Like others have said, oftentimes the bolt corrodes to the head where no threads are present. If the head and bolt move together, you will know that the shank of the bolt is corroded to the head.. If so, reheat the head and try rocking it back and forth with the mallet until it loses its grip on the bolt…
