Cooling Woes ! Help !

[Racegem]

You're both sort of right.
Without a thermostat, the engine will take a lot longer to heat up. But... when it does get hot, it won't cool down as the water doesn't stay in the radiator long enough to cool.

[Loz]

Just remember that when the thermostat is fully open, usually about 85-95odd degrees, it barely restricts any flow through to the radiator, and as normal operating temps are about this or a bit higher, they only aid in a quicker warm up.
The real change in coolant flow comes from the speed of the engine, as that drives the pump, and at the slow idle speeds they are no where near as efficient as when they are spinning faster. So when you stop not only do you not have the airflow from moving, but the pump is turning much slower.
There is only a certain amount of heat that a radiator can take out of the coolant, without help from air flow. And if the water is hanging around the engine too much, it is heating up too much. If the water is flowing faster, it doesnt have the chance to heat up as much. The, temp drop accross the radiator is pretty much constant with no airflow, so that it can only take away more heat with added airflow, hence the reason a car is cooler when moving (and that the pump is working more efficiently).

[Thirsty]

Race gem is right but consider this.Thermostats also help with the coolat inside the block.
Without one the water takes the quickest route through the block and doesn't correctly cool the rear of the block.
Number 4 cylinder therefore suffers with heat and will mean if your engine is a litte sus the first thing to stop doing its job is the number 4 cylinder and bore and piston.
Thirsty

[Loz]

I disagree. The thermostat doesnt provide enough flow resriction to make a difference. And in terms the block, straight after the coolant leaves the pump, the coolant goes up through the block through all cavities. The passages arent large enough for the pump to pump all of the coolant straight up past number one, or even number 2 cylinders, and out through the thermostat back around. The pump is sized correctly so that is cant cant flow a small enough volume that this happens.
Again, all a thermosstat does is restrict flow until the engine is at operating temp, and then when fully open does NOTHING...
Why then dont race cars run thermostats? Wouldnt they need the added protection of cooling their bores that are away from the pump?

Loz

[Stock TE]

I know a few with race cars that do use thermostats.