It always amuses me to go on a vintage car rally, and see drives leap out and top up their radiators, and then the next mile it blows it all out the overflow until it establishes the running level again .

Overflow tank not needed. The top tank is not supposed to be full. Actually, if the fluid just covers the tubes with cold engine it works perfectly.

Make sure you have a 160 degree thermostat in your motor for if not water is traveling too fast and fills the top tank and then out the overflow. Water is suppose to move slow to give radiator time to cool the water. Walt.

I use a 180 thermostat at 90 degrees with no problems. Once the thermostat is open the water obviously flows at the same rate regardless of the thermostat rating. In hot eweather the water temp is going to 180 or higher regardless of the thermostat. Also, serious research has proven that moving the water through the radiator fast provides the most cooling. Only logical. Keeping the radiator hot means the most heat dissipation.

Just a thought: If "overflow" tanks aren't good, wonder why most cars/trucks built in the last 20 years have them ??
What is wrong with them on 'early' cars; keeps air out of the radiator ~~

[quote="Richard Dryman" post=6170]Just a thought: If "overflow" tanks aren't good, wonder why most cars/trucks built in the last 20 years have them ??
What is wrong with them on 'early' cars; keeps air out of the radiator ~~

Because modern radiators are of the cross-flow variety, as opposed to the down-flow versions used on the older cars. Also due to modern cars having low sloping hood lines there isn't any room for a top tank on a down-flow radiator, so thus the need for a separate expansion tank.

I still like the extra quart+ of coolant in the radiator and no air. But, each to his own

I wonder why all race cars slow their water system down. I know as when I was racing dirt modify's we use to cut impellers off the water pump. Slow your water down. My 53 Hornet has my set up and I can travel 500 miles a day in 100 degree weather. Walt.

Although most racers thought the water didn't have time to cool...They actually slowed the flow down to prevent cavitation at the pump. The restriction only works when put on the outlet of the pump. Not my opinion, but this is the result of extensive research by Stewart Water Pumps (sp?). He built a water pump dyno out of Lexan to actually see what was going on ! By the way they supply NASCAR racing teams.
Don't believe it? Try putting the restriction on the outlet of the radiator and see how fast the engine overheats. I did. It took two laps at speed on a 3/8 mile asphalt oval with a fairly stock Chevy 350. I think we were using a 22Lb cap too.
Also the OEM overflow tank on my Chevy van works just fine with my OEM vertical flow radiator. Saves a lot of coolant and I don't have to check it nearly as often.(sometimes not often enough!)LOL