Quote:
Originally Posted by MAXUM
Hard to get into the heads of the engineers that design these things, I suppose there is a legit reason why they did what they did. My initial guess is they need to pump a larger volume of water through those big block engines to keep the operating temperature where it needs to be. I wonder why not use a closed loop cooling system with some sort of heat exchanger unless it's just plain cost and weight prohibitive.
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The alpha was used with a big block in the past so it moves plenty of water, it's just a very different pump design that moves much more water per revolution thatn the Bravo pump because it is turning at a lower speed. If you try to spin it really fast, the vanes will probably flex too much and make it cavitate.
Alpha impeller
Bravo impeller
Closed cooling is an option on most marine engines, people just tend not to want to pay for it. Either way though, you still need a raw water pump to pump lake water through the heat exchanger.
Edit: One other thing I wanted to note, I am pretty sure the Alpha impeller is a a centrifugal pump and the bravo is a positive displacement pump. The Bravo pump requires that the vanes be flexed substantially on every revolution, as they get squished, volume is lost between each vane and that forces water out of the pump. The Alpha pump, if memory serves, just flings the water out with centrifugal force. The vanes are not nearly as stressed.