Ruby Radiator Water Level

[Steve Jones]

I fear you're getting misled by what happens in a modern, pressurised and pumped, system. Your Seven has a thermo-syphon, unpressurised system with no pump. As long as the water level at any time is above the radiator core all is well. By how much it is above is down to the level the engine/radiator sets for itself. All that happens when you top the radiator up above this level is that the excess is expelled via the overflow until the correct level is regained. If you then top it up the process is repeated. As a general rule, if, when cold, you poke your index finger down through the top of the filler neck and it just touches the water level then everything is as it should be. Calculations involving volume, power and measurements don't affect that in any way.

Steve