In the original thread where this got started, Ronbo posted this:
"GM's research was specifically to address coolant issues with high horsepower engines being developed for the Corvette. (not that high horsepower engines have anything to do with Cobra's) Since emissions dictate not running rich (which would lower detonation problems) they addressed the "real" problem: the steam pockets that develop in any engine's coolant passenges above the cumbustion chamber. (turns out steam is a lousy conductor of heat, go figure) The problems you stated ie: valve spring fatigue and cylinder bore wear are a direct result of combustion chamber temps, not block temp.
There is a huge difference in your cumbustion chamber temp and your coolant temp. Why do you think your recovery tank level varies so much between hot and cold (the liquid coolant only expands slightly) that's how much steam is in your cylinder heads and upper block."
Thermal coefficient of volume expansion of water is 0.00207 per deg C.
My source:
http://en.wikipedia.org/wiki/Coeffic...rmal_expansion
Figure 90 F to 200 F temp change is 110 F or ~61 C.
The volume change is 12.65% when you do the math.
Figure a 3 gallon system or 12 quarts and the volume expansion is about 1.5 quarts.
Now since the radiator starts at zero pressure and may end up at 12 psi at temp the expansion may be slightly less, but water is not very compressible.
The statement that water does not expand very much and this is steam, does not stand up to the science. Although there may well be some steam generated in the heads, it has to be small bubbles and not a large pocket or the over flow tank could not hold it all.
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