My 1966 Impala 396 will sputter and sometimes cut off after cruising around 55mph for a while during the hot weather. It happens when I exit the highway, depress the clutch and go to neutral, and come to a stop at the stop sign. For now, I can usually get it to start back up again but feel like eventually I may get stranded. I adjusted the carb to idle a bit higher but this does not seem to help. I have read a few places this was due to high temps in summer ( usually around 90 to 95 degrees here). Any thoughts? Ideas on what this may be?