Is there a maximum recommended RPM, for the pump itself, not the engine?



Lawrenceville, GA

I dont think there is for the water pump but my brother has told me stories about slinging the windings out of generators by over-revving them, I haven't done it yet which amazes him although I have revved the girl pretty high, missing shifts etc.I do know that if you over tighten the belt you are asking for premature wear of the bearings in the pump and generator/alternator. 1/2" deflection pushing on it with your finger is what the manual calls for.

55 Vicky & customline

58 Rack Dump, 55 F350 yard truck, 57 F100

59 & 61 P 400's, 58 F100 custom cab, 69 F100, 79 F150, 82 F600 ramp truck, 90 mustang conv 7 up, 94 Mustang, Should I continue?

On my race engines I have always set the water pumps up to be underdriven.  Turning a water pump at higher revs does two things 1.) moves the volume of water faster through the cooling system giving the coolant less time for heat transfer; 2.) there is a good chance that the pump could cavitate and reduce cooling capability.  Normal street driven engines live around 2000 rpm.  I size the water pump pulley to operate between 2000 and 3000 rpm of the mean engine operating rpm range.

It's for street use that will be raced on occasion.  With the stock pulleys, the water pump is about 10% underdriven.  I might just make it 1:1 for a little more flow at idle.



Lawrenceville, GA

Hi Charley!
I'd say you ought to use "whatever works" on the street - then loosen the belts a notch on race day!

 
 Steve Metzger       Tucson, Arizona

In discussing this with Charlie offsite, Charlie came up with the following from  the Stewart water pump site.  http://stewartcomponents.com/index.php?route=information/information&information_id=8

Lorena, Texas (South of Waco)

Going along with what Ted Eaton said, I read an article a few years back while fighting an overheating flathead. The article was by an engineer that specializes in cooling for NASCAR. The old thinking was that too much flow didn't have enough residence time to absorb the heat in the block. But, he went on to say that more flow with cooler water worked better. The problems with high flow, particularly on a flathead, was the low operating pressure. At high flow the cap would "burp" due to turbulence and effectively lower the system pressure which in turn causes a lower boiling point. The lower pressure/boiling point then allowed steam pockets which don't cool well so the heat would rise and cause more steam pockets which cause more heat and it goes on from there. Also, water pumps being centrifugal as opposed to positive displacement can only developed a maximum flow/pressure and then flatten out. Once you reach that flow/pressure, there is no gain by increasing the rpm. There could be more parasitic loss, but I doubt it. The pump at this point will be cavitating though and that can be detrimental to cooling. Hopefully that makes some sense.

Life isn't about arriving at the end in a pristine, well preserved body; It's about sliding in sideways, all clapped out, yelling "What a ride!"

It may not be right but I could not keep my stock 56 292 cool when idling at stop lights. I added the largest stock style radiator and it made no difference. I took to running the engine in nuetral at stop lights to help. I added the upper shield so all the air would go thru the rad. I plugged the bypass and drilled a 1/8" hole for some movement of water, nothing helped. One day I had the cap off and looked at the water when idling there was no movement of water. With a slight raise in rpm there was movement. I decided I needed to speed up the pump and bought one for a Mustang 302. My problem was solved. Greenbirds said on another thread that this was a way to fix the problem. Ted wrote there were many different sized pulleys and that stands to reason. I now need to replace the 6 blade fan with something less. The most I ever drive is 65 on SoCal freeways so I don't think I'll ever over speed the pump. Good luck

56 Vic, B'Ville 200 MPH Club Member, So Cal.

In my own collection of stock water pump pulleys, the cars have the biggest and are underdriven (turn slower than the crank) while the trucks are smallest and are overdriven (turn faster than the crank)
My temps do creep up in summer traffic but I have never overheated.  I'll need new pulleys to complete another project so it's a good oportunity to tweak the water pump drive ratio as well and see what happens.




Lawrenceville, GA