[Excaliber]

Some T-Stats come with a hole in them all ready, others not. It's just to allow a little circulation through the hole. I've never heard of it being for a "vapor lock" situation. The hole sure makes it easier to bleed all the air out of the system before the T-Stat starts to open. Drill a small hole basically anywhere in the body/flange of the T-Stat just being careful not to hit anything else (like the thermal sensor).

I've heard that "theory" about slowing down the water flow by using a T-Stat and thus keeping the water in the radiator longer. I've also heard of high volume water pumps that move more water. The two theorys are opposed to each other, in my opinion. Some people who don't run a T-Stat use a restrictor that is basically a T-Stat with the center drilled out. This restricts the water flow to some degree and mimicks an open T-Stat.

I suspect "slowing down the water to keep in the radiator longer" may work on some systems and won't mean squat on others. Like wise a "high volume" water pump. THAT will sure work if your old water pump has worn out impellers and couldn't move enough water to begin with, but then again a new standard pump may work just as well.

It IS a good idea (generally speaking) to run a T-Stat to keep the engine temp from staying to low. Many "race cars" don't run them because it's no problem getting at or above operating temp anyway! Formula Fords (for instance) do not use T-Stats and typically run 200-210 during a race, so they don't need one.

I've run with and without one in my 427 FE side oiler. The ONLY difference it makes is on a "good day" my engine temp gets to low. On a hot day with the T-Stat open it makes no difference. IF the car is going to run hot (200-210) it will run that hot with or without the T-Stat.

Strangely enough, advancing my base timing has helped not only my idle and cruise performance it ALSO lowered my engine water temp!