[jugger]

I am changing out my water pump on a ford 302 engine; this is for street use. I see "high flow" pumps advertised. I ordered a stock w/pump from NAPA and the impeller is 3-7/8" in diameter. On a high flow w/pump that I was interested in, the impeller is 3-1/2" in diameter.
1- is the impeller the main determinant of higher volume flow or
2- does the design and materials (billet, etc.) make more difference?

I would think that since the pulley (and hence rpm) is the same for all units, that the larger impeller is the most important consideration for street (stop and go) driving and that in a race situation, a smaller impeller would be more appropriate for high revs.

Can someone please educate me so I know what to look for?

Thanks.

[techinspector1]

Jugger, you've made me realize that I know little or nothing about high-flow water pumps even after being in this hobby for over 50 years.

I will share with you what makes sense to me. Filling the pump cavity with as much impeller as is possible makes sense. Making sure the impeller is a tight fit on the driveshaft makes sense. Using a solid sheet metal backing plate on the impeller to prevent water from circulating inside the pump cavity makes sense. Possibly increasing the drive ratio off the crank makes sense.
I figured out one time that the pump is driven at about 1.2 to 1.3 times crank speed on OEM applications. Maybe a guy could try 1.4 and see what happens.
Color me fairly clueless.

[GMCTRUCKS]

My buddy put one on his Burb well when seeing the better flow I said let me get one as well because one I have underdrive pulleys and this stop & go traffic here in Houston sure can get to ones engine now I have had them on my truck for a while and im super happy with them.

[jugger]

Thanks for the comments. I guess a common sense approach may be the answer although one would think that the angle of the vanes on the impeller could be at issue besides size, however, none of the pumps that I see advertised amplify on design and I have nothing to compare my stock pump to, so I guess I have to take the word of the advertisers coupled with common sense. Taking that one step further, I would surmise that increasing the turning ratio might prematurely burn out the bearings if it turned too fast all the time (in traffic) and like a marine propeller, could cause cavitation or other unintended consequences.

I know there are experts out there who can shed some light on this issue and would appreciate their insight.

Mahalo.

David