uninteded acceleration?

Happened to me in my 64 sport fury. At a stop sign, stopped, gave it a little gas to creep up a little, the throttle return spring let loose, floored it! Shot across the traffic lanes no way brakes would hold the 426! Shut it off and it dieseled for like 20 Seconds, had to close the throttle plates by hand under the hood to get it to stop. **** my pants!!!