Car starts first crank cold every time. Car runs for an hour. Shut car off. Car will sputter when trying to restart and then stop firing entirely until the next day. Any ideas? Also, the car will not accelerate in third gear at all. It won't go any faster than about 40, which is achieved in second and held in third but nothing more, even on flat land. Downhill it will get to about 50 or so but once the ground levels out it falls back. I'm suspecting ignition advance or electric choke. Carburetor is freshly rebuilt, it's barely done 10 miles since being fully rebuilt. It will overheat sometimes but I get the feeling it needs a coolant flush and a new expansion tank, which I already have. 40,397 miles.