The stock water-pump pulley arrangement is inappropriate for constant
high RPM ,the biggest drawback is the stock water pumps are designed to
operate at relatively low speeds, as a result,the standard impeller WILL
cavitate-churn coolant rather than push it through the cooling system
when spun by stock pulleys at high revs(5, 500and6.000rpm).The water
hoses are a clue to whats going on inside the waterpump,When the
impellers starts to cavitate,the hoses  jump around due to turbuence
caused by cavitation and the resulting aerated coolant,Racing
beat/mazmart/mazda offer a number of pulley combinations that will slow
water-pump speed suffiiently to avoid cavitation and  also slow down the
alternator,as the alternator is overdriven by appropximately 33%-if the
engine is turning at 6.000rpm the alternator is spinning at 8.000rpm,

robert pay rotary owner from the 1970s/02/07,

I think that is an urban myth Robert. Not what we found with
our water pump dyno. No cavitation at up to 7000 RPM as I recall.
You need a lot of water flow to cool an aircraft engine
as it runs 150 HP all the time. A car is lucky to see 40 HP
all the time. Might be true on an 11,000 RPM race car engine.
It will cavitate if you let the water level in the block get too
low.

Paul Lamar ...No rotor no motor.

Isn't that cavitation erosion in the two water pump pix?

Doc Custer
Retired Software Engineer and sometime Audiologist

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Yes caused by low water level in the engine.
Note the dividing line is horizontal.

Paul Lamar ...No rotor no motor.

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