As far as I know, Andy Black is the only City player to have headed a goalkeeper's clearance straight back over the keeper's head into the net.
In a match v Charlton in 1947, Sam Bartram ran out of his area to boot a loose ball clear, but didn't get much elevation on the ball and hit it hard about head height straight to Black. He bravely headed the heavy old leather casey back over Bartram's head from what must have been about 30 or35 yards.
Black later ran a pub at Moss Nook and I think there was a cartoon of the incident on the bar counter.