That's quite the surprise. Japanese engineers are expert at making sure the design has extra safety margin. Even back in the 70's. Although they are much better at it now. I can't imagine they are rpm sensitive 33 years later.

 

I have heard of a lot of guys adding flow restrictions on pump inlet, not aware they are increasing pressure drop. Particularly true with fuel systems.

 

-al wick

My pump outlet has a 5/8" hole restrictor on the outlet. Same two water pumps for 9 years. Shifting at 9,600 RPM. No cavitation damage at all. Generally the radiator(s) will be enough restriction to keep the pump well below its top flow rate, and lowest inlet pressure. If there is little or no restriction on the outlet side, the pump might cavitate momentarily during acceleration.

 

More likely with lower total system pressure, and low restriction. Less likely with an accumulator system and more restriction,and higher system pressure. Less likely with low system volume. More likely with high system volume. With just a bit of anti freeze and its anti foaming agents, very unlikely. More likely when air remains in the system. The pumps are mounted high on the block, and will not pump at all with a bit of air sitting in them. It is critical that the pump be submerged prior to start up.

 

Lynn E. Hanover