opinions needed on this idea
The statement "water flows too fast thru the radiator to have time to cool" is commonly spread among hot-rodders. It has no basis in science (my M.S. thesis was in heat transfer). An engineer at Stewart ran across this and was so amused that he ran down the source (
Stewart Components). The idea came from vintage cars (1920-20's) where a weak radiator cap spring would burp fluid due to increased flow pressure of a tuner water pump. A restrictor fixed that, but the guys mis-understood why.
As mentioned, you can buy an IR gun at Harbor Freight for $25 on sale. Mine works amazingly well against a mercury thermometer when checking T-stats in a pot of hot water. Running w/o T-stat wouldn't prevent over-heating unless it gives too much restriction in the "full-open" position (unlikely). It will over-cool the engine in the winter. Don't buy a "fail-safe" T-stat since they permanently lock open if you ever over-heat.