That must be the oddest thing I ever read.
While a lower than normal float level setting,will affect the A/F slightly, at idle, it's common to just, adjust the Mixture screws a little richer to compensate. Cuz if you don't, the engine will idle crappy. But if it doesn't idle crappy then the screws were probably too rich in the first place.
Then theres the main and power circuits; These circuits are probably the least affected by a slightly reduced float level.
And the Transition circuit. This circuit is likely the most affected. If the level gets too low, you will introduce driveability issues ;such as hesitation on tip-in, perhaps a bog, or poor transition between circuits.
Now, I have no idea where SGV is, or what your altitude is there. But the thing is this; if your altitude is different than what the carb was calibrated for, then a float-level tweak may actually be beneficial to your engine.
And the clincher; changing the float level should have absolutely nothing to do with the minimum engine running temperature. That is the job of the stat.
However;If the float level was very much too high, I suppose it could be possible for fuel to get into the engine elsewhere than through the proper circuits. If this happened, then the extra fuel will, for sure, suck heat out of the chambers. It will also cause; a poor idle, a lazy engine, cylinder wash, terrible fuel mileage, an ever increasing "oil" level as the gas ends up in the pan, and makes-your-eyes-water exhaust stink.
Finally; just as retarded timing can put heat into the exhaust pipe, due to the charge continuing to burn there, an over-advanced timing can put extra heat into the cooling system, due to the extra work being done trying to compress an already expanding charge.
Bottom-line is this; it's a poor practice to try and control cooling system temperature with float level changes.
My experience with my slanties has been that they naturally run cool. A new stat may not run at its advertised temp. They have a fairly broad working range. And you can't mod them. You may have to buy several and boiling-water test them. Do not let them fall to the bottom of the pot during testing, to sit there next to the heating element. Stants are usually pretty good.
And, of course, timing. Give that baby what she wants. Idle timing, Power timing, Rate of advance, and most especially the vacuum advance. Oh, and make sure the valve lash is adequate. A tight lash will make a rough idle.
