318 water pump question

I'm going to replace the water pump on the 318 going in my 48 Dodge. I've discovered there are 6 vane and a 8 vane water pumps.
Is one better that the other? Was the 8 vane for an a/c car? Thanks

 

Ya know, I've changed probably 100 or more water pumps on 318s and other small block Mopars. Through all that time, and all those pumps, I don't ever recall even looking at the number of vanes on the water pump.... My guess is it just didn't make that much difference. But then, I didn't know until a few short years ago that there is actually different starters for small block and big block Mopars. The armiture end of a big block starter is suppose to 1/4" longer then the armiture end of a small block! For the record, that 1/4" didn't seem to make much difference either. Gene

 

I don't know about the vanes, but if clearance is an issue with your swap, you can use the older (pre 68 I think) cast iron water pump, as it is several inches shorter than the later aluminum ones.

 

ac/ non a/c
car and truck

and older had less vanes
the dia of pully should relate to pump vane count ???

 

just did a water pump on the 79. asked for the truck ac piece and when i got home i realized that it was the same as the hd police model. as far as i know there is only 6 vane units. the hd police units can be quickly id'd by the tubes surrounding the shaft on the outside of the pump. non police unite have fins instead of tubes. dropped my temp approx. 15-30 deg.(stock gauge with no temp marks other then a normal range.) i just reused the stock pulley on mine.

 

the ac pump is much heavier duty (note the reinforcing around the bearing area) and flows more water than the std unit...the std pump will not last 2 weeks on our dirt track motors, but the ac pump is good to go and runs cooler...

 

My 318 squad engine came with an 8 vane. Seems to me the heavy-duty applications used the 8 vane. For a daily driven vehicle, the 6 vane will work just fine.

 

aluminum pump had the water inlet on the p***. side; the irone one had the inlet on the driver's side