[scottj]

Leaving the thermostat (or restrictor) out won't cause the coolant to flow too fast through the radiator. Nobody even makes a water pump that will flow too fast. The faster you can flow the coolant the LESS likely you'll be to develope hot spots and steam pockets. That's why the makers of performance water pumps, like Edelbrock and Stewart, develope their pumps to flow as much as possible. And it is why they don't recommend underdrive pulleys or restrictors. It is also why the Robertshaw high-flow thermostat exists.

Leaving the thermostat out can cause it to run too cool though.

Putting one in can cause a race motor to melt down if it sticks shut, so many builders leave them out of race engines.

Scott

P.S. Running without a restrictor isn't damaging, but misinformation can be.