Holley idling issues

Hello all, I have a 500 ci (440 stroked) with a 950 Holley. I noticed the idle after a long drive, spikes to 1100 rpm in neutral, it is typically set at about 750 in neutral. This only happens when the car has been run for a long time. When the car cools down, the idle will go back to 750 rpm. Any thoughts?