Update on temperature problems: first, in answer to Rod's post; when the car was at Euro Motorcars [
!], the removed the radiator and sent it to a shop of their choice who "allegedly" hot tanked it. This was not adequate. When we took it out, the radiator shop of my choosing (Winegardners here in Annapolis) found that the core tubes were clogged. We tried to get a new radiator- an aftermarket one purchased by mail did not fit the car, and the parts seller paid for it to be returned and will credit me for it. I ended up ordering a high-performance core for the old radiator and having the old radiator 'rebuilt' using the new core and old tanks and straps. The new core is still two rows of tubes, but they are closer together and the fin count is higher per inch. It fits fine. I am picking up the car tomorrow. According to the shop (AutoShoppe in Silver Spring) it runs fine and stays cool. They also put in the Crane ignition conversion I had not gotten around to doing.
I think the infrared noncontact thermometer that I bought is one of the most valuable and interesting tools I have ever owned. For example, on a hot Maryland day, the pavement temp on asphalt is about 125 degrees. You can see why a car driven at relatively high engine speed on a road that hot would have trouble cooling if any part of the cooling system was not at top performance. The air coming in through the radiator grille is already very warm. Heat, of course, will run down its' concentration gradient regardless of which medium the transfer is occurring through, and the hotter the air that you are using to cool with, the less cooling you will get.
I find that the first year with a 'new' old car is the one in which you get everything sorted out. I am looking forward to having the end in sight with the 280SL- if the recent work sorts out the cooling, then we will have the rear axle ratio change yet to do, and removing the modern radio and putting the old one back in, and maybe a set of shifter bushings. Oh yes, and heater levers. After that, maybe things will settle down a bit. The car is such a pleasure, though, that the improvements are worth it.