2 core rad

[Synchro909]

Originally Posted by Hoogah

If you’re not having overheating problems, maybe you don’t need to do anything. If it ain't broke, don't fix it. I agree with this part of your post It could be that you’re just pushing out excess water until the rad finds a sustainable level. A cheaper way to reduce the overflow might also be to grind back the water pump vanes or even replace your pump with a modern one that has smaller vanes. This aprt I don't agree with.

In a Model A, you don't need a water pump at all. Thermo-siphon is enough as was proved by a Queensland guy who drove from Brisbane to Darwin for the National Meet with a broken water pump shaft. His car ran warmer than usual but there was no harm done.
As for playing with the amount of water pumped, it is irrelevant. So long as there is nothing stopping the water flowing altogether and the radiator is in good condition, as shown by the above example, things will be fine. Contrary to what many say, it is not possible to pump too much water. Once the radiator has "found its level", water will circulate at what ever rate the pump is capable of but never too fast. The ONLY place the water pump can get water to pump is from the bottom of the radiator. A restricted radiator will automatically restrict the amount of water the pump can move so it can't pump more into the top tank than it takes out of the bottom tank. Overflow because the pump is moving too much water is impossible. Once the radiator has found its level, nothing will change unless there is another problem like a blown head gasket.