Hailwood finished 15th , Surtees 17th and Posey retired with piston failure .
Two changes followed , Stommelen was replaced by American Sam Posey and Hailwood returned to join Surtees before the United States Grand Prix .
Hailwood finished 15th , Surtees 17th and Sam Posey retired with piston failure .
Two changes followed , Stommelen was replaced by American Sam Posey and Hailwood returned to join Surtees before the United States Grand Prix .