190 to 200 driving down the highway is to hot. This leaves you no safty margine in traffic on a hot day. A hot day is over 90. When moving above 25 miles an hour you have the forced air from the forward motion of the car cooling the radiator. There is a differance when heading into the wind which cools better even though it takes more engine power than with a tail wind. I find unlike some others that faster speeds don't mean higher temperatures. I drive at 65 to 70 plus and on a two day 1,200 mile drive 2 years ago with temperatures over 100 both days it ran at 175 to 180 at highway speeds. I didn't have any overheating in towns but had problems with the new gas a few times. When I say over heating it never got over 200 in towns. Everything on my 39 convertible is stock except a working pressure cap and Skips pumps. Modern stats don't work in these engines when it gets over 85 outside temp. The flow opening is to small and causes overheating from less water through the radiator when it's hot out. Skips pumps provide almost double the water through the radiator and entire system. I have installed Bob Shewmans 180 degree stats in my 39 conv.and 39 P/U and have been running them for over 4 months and both engines are right at 178 to 181 every time I check them. The hoses have a 1 3/4" ID and the stats heve at least a 1 5/8" ID opening so no noticeable loss of flow is indicated as far as temperature rise. Bob's stats sit in the hoses and are held in place by the radiator output necks and can't move. Bob can be contacted at 1-610-933-6637 or
[email protected] I also find the engines run nice and smooth at 180 and get up to 180 in about 5 miles. After the stats fully open at 180 they stay wide open and act like they are not there, the same amount of water flowing through the system as if it didn'thave stats. If the temperature drops below 175 the stats will partialy close until the water gets to 180 and open again. This would be a continious cycle at say 50 degrees out to keep the engine at 180. The real problem with stop and go or slow driving in hot weather is the design and on some years the location of the fan. The stock 4 bladed fans provide a boarder line amount of air, the crankshaft mounted fans move air against the front engine like hitting a stone wall. G.M.