Does This Debunk the "Coolant Can Flow Through the Radiator Too Fast" Idea???

Does This Debunk the "Coolant Can Flow Through the Radiator Too Fast" Idea???

Aw, what the hey, since this is the thread that never ends, eh!

Dave999 said
Larry Shepherd in his how to build mopar small block engines book goes into details about how to reduce pump speed for high rpm engines, stating that for ideal cooling the pump must run at nearer to standard speeds, or you will overheat when you convert your small block into High rpm race engine. Gives part numbers etc to get ideal pulley gearing for RPM range, doesn't explain why,

As you said later in your post, it's because excessive pump speed ➙ cavitation ➙ reduced pumping efficiency ➙ overheating.

Dave999 said
It did not explain that a pump that produces a higher pressure in the system could be a problem

…because that's not a thing. The water pump doesn't produce pressure, it just circulates coolant. There'll be a relatively minor amount of what is called "head pressure" downstream of the pump if there's a flow restriction, or a large amount of head pressure if there's excessive restriction due to a clogged radiator, blocked hose, thermostat stuck shut, etc.

But under normal conditions, the cooling system is pressurized not by the pump, but by steam. That's unless you are running waterless coolant, which generates no steam, so the system runs unpressurized…even though the water pump is spinning like the Tasmanian Devil in old Warner Bros cartoons.

Dave999 said
modern radiators have their filler cap/plastic bottle plumbed in to the lower pressure side of the system before the entry into the water pump at the colder end of the radiator

Some do, some don't. Many still have it the other way.