[andyleonard]

One of the things that frequently gets missed in this traditional cooling system discussion is the end use of the vehicle. The conditions of a street cruiser in Vegas are very different from those of a road racer.... and the car's use must be specified or else something that is a very good idea for one driver will be dismissed as nonsense by the other.

An example is changing the pulley ratios for a street driven car to increase the water speed and volume at low rpms...giving the same result as a "high performance pump" for the cost of a pulley. Or equally, changing the pulleys for a road race car to slow the waterpumps and keep them from being overdriven and cavitating. I'm learning everything goes to hell when a waterpump impeller exceeds 7000rpms.

I believe the "myths" about restrictor discs and "grinding off every other vane" originated from problems that occurred when roadracing stock cooling systems at continuous high rpms and forcing the caps - which for a long time were located on the radiator itself or more recently on a tank in the "pump-out" side of the system - to open from water pressure (not heat) and lose coolant, which then caused overheating.
Slowing the water flow (pressure) by laming the pump and/or restricting the flow kept the water in the system and that kept things cool. Now that we have figured out that what we really want is an overflow tank/cap on the "return" side of the system where the cap can't be exposed to sudden slugs of high-pressure pumped water, we can block off all other caps and run a high-pressure pump and a very high pressure cap if we like. They didn't get that far back then.

But back in the day, with a 4# cap on the radiator and no overflow tank, I'll bet the boys running 'shine at 5000 rpms ground off those pump vanes and stuck those restrictor washers in there because it worked.