Block heaters are awesome. I had one when I was stationed in Canada, and got to -40 below many times. First time I plugged my car in at nite, went to unplug it in the morning, grabbed upper heater hose to see how warm it was, well it wasn't warm but F'n HOT!!!!! left red mark on palm of my hand. Car was a carb'd 350, no choke, and would start just be turning the key. I would start the car, turn heat on hi, get out to unplug/take care of cord, buy time got into car was pretty much warm inside. I think it heated to 120 or 130. It was a truck unit I think, my dad got it for me and installed, one end went into a soft plug, other into radiator I think. Had a pump that circulated the coolant.