440 adding a vapor return line?

ok so I went to the track yesterday it was hot...along the way the car ran good for about 15 miles temp 190.. in traffic temp got to 195 car dies, 850 dp holley mech fuel pump return line to the tank...pop the hood no fuel press...hold it to the floor it starts runs another 6 miles to the track gate dies again...did the same thing..held to the floor started got me in...when the sun went down, drove all the way home very little issues.. thoughts ideas.... the intake still has the exhaust dross over under the carb non blocked..alum rad hood scoop..air movement under the hood seem good...