I have a 5.0 stock water pump on my engine...I was told recently that the pumps work best at lower RPM's and since my car is mostly in the 3-4K range (except when I cruise on the freeway) should I be changing the water pump? Any recommendations? I had an edelbrock water pump but wasn't too happy with it....
Are you having any cooling problems? If not, just go ahead and use the one you have. If that isn't adequate, you could look into a high performance unit. Milodon makes some decent units. http://www.milodon.com/water-pumps/water-pumps.asp
I liked my E-pump, it keeps a constant flow rate (RPM not a factor). http://mmb.maverick.to/showthread.php?t=78869 ...:Handshake... John has the same pump... http://mmb.maverick.to/showthread.php?t=75605&page=400
The stock pumps come in three flow rates. A "high Performance" pump usually means it's got a small impeller for high rpm running. The medium impeller is what most come with, std flow for most applications. The large impeller pumps are what you get when you specify: Police, Taxi, Extra cooling, A/C, etc. I'm running one spec'd for a late 88-up Crown Vic, looks exactly like the one you posted the pic of here. The earlier pump is cast iron (up to mid 88)
I used to worry about matching the pump to the intended rpm of the specific application.. but now I just use pulleys to better control the rpm of the various accessories and typically just go with stock units on anything short of full race. Now, with that said.. there can be slight power gains in the upper rev range from going with a higher rpm type pump(as baddad already pointed out with differing impeller designs).. but.. the underdrive pulleys are where the bulk of the tuning/power savings will come from. Trick is to not get too crazy with the underdrive ratio of the crank pulley or you may end up with charging issues if you idle around town a lot at night with lights on. If you buy complete kits then you're pretty safe in that everything is matched.. buying separate components is where you can run into issues sometimes. And e-pumps are certainly worth power if you're trying to finagle those last few horsies out of the motor. Basic rule is.. the higher you spin it.. the more you save over a mechanical pump.
Personally I'd just go with an electric pump like CSR, Meziere or Moroso. You don't have to worry about any pulleys or belts and can switch it so it automatically comes on were you set it, or you can manually switch it. Just pay attention to the GPH they advertise, the faster you push water through the motor the less time it has to cool........................IMHO
