Water pumps

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1wild&crazyguy

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Ok there are 2 small block replacement water pumps available, a 6 blade and an 8 blade.

The six blade was standard and the 8 was for AC cars/trucks/vans.

Mopar says 6 blade for iron head drag racing for obvious reasons like parasitic drag and cooling/heat transfer time with high rpm in mind, not really cavitation though, i don't think.
I run a 6 blade in the 340 but am going with the 8 blade on the 410 stroker with the idea of better cooling at lower/idling rpms, and it aint gonna rev where the 340 does anyways.

So who runs which and in what/why? or did you go after market & why?
 
On the outside there is a visual diffrence to them,one looks like they milled away the cooling holes that go around the shaft that is the high flowing one,On my 340 in the duster I tryed it and had overheating problems,when I changed to the older style I have had no problems,I run a 195* thermostat and the car stays at constant 190* in florida hot wheather
 
waggin said:
On the outside there is a visual diffrence to them,one looks like they milled away the cooling holes that go around the shaft that is the high flowing one,On my 340 in the duster I tryed it and had overheating problems,when I changed to the older style I have had no problems,I run a 195* thermostat and the car stays at constant 190* in florida hot wheather
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So you run a 6 blade water pump?

Are we talking bigger but fewer blades as opposed to many but smaller blades?

I should have done a side to side comparison, but yes the 6 blade has the tubes around the bearing cause they were there to support it better for the cop cars/hd they came on, supposedly. But I figure the AC drag would constitute more volume/flow to keep it the motor cool.

what do you think?
 
I really never counted the blades but another member pointed out the diffrence to me a few years back and called one a high volume and the other a standard.I would say the idea is to slow the water down for more cooling time in the radiator,you know how cooling issues are,sometimes you have to try diffrent stuff.the low volume pump did the trick for me,I'd start with the low volume pump but this is just an opinion and the experience I had.hope it's helpful to Ya!
 
I run the 8 blade because I run the March power and amp pulleys that slow down the accessories. I first had a 6 blade on it and it didn't actually overheat but it did run kinda warm idling in town (200~205*). Switched to the 8 blade and runs cool all the time now (never more than 190*). The blade diameters of each are the same. Just more blades of the same size spaced closer together on the 8 blade. I also run the flow cooler disc on the back that's supposed to help with cavitation.
 
Iron heads you can slow it down to an extent while aluminum can move faster through the passages with aluminum's faster heat transfer.

I'll just find out then.
 
fishy68 said:
I run the 8 blade because I run the March power and amp pulleys that slow down the accessories. I first had a 6 blade on it and it didn't actually overheat but it did run kinda warm idling in town (200~205*). Switched to the 8 blade and runs cool all the time now (never more than 190*). The blade diameters of each are the same. Just more blades of the same size spaced closer together on the 8 blade. I also run the flow cooler disc on the back that's supposed to help with cavitation.
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I was thinking about making one and tacking on the impeller blades too, right on.

Thanks for the info.
 
fishy68 said:
I run the 8 blade because I run the March power and amp pulleys that slow down the accessories. I first had a 6 blade on it and it didn't actually overheat but it did run kinda warm idling in town (200~205*). Switched to the 8 blade and runs cool all the time now (never more than 190*). The blade diameters of each are the same. Just more blades of the same size spaced closer together on the 8 blade. I also run the flow cooler disc on the back that's supposed to help with cavitation.
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Tracy, any pictures?

I'm thinking of changing my WP since mine likes to heat up idling, don't know how many blades but is for factroy AC
 
Sorry Larry I don't have any pics. If yours is for an A/C car it should be 8 blade. I'm nearly positive all A/C cars used an 8 blade pump. You might try a Flow Cooler disc on the back of the water pump impeller.
 
fwiw My 410 stroker with higher compression than my 340 ran cooler with the 8 blade a/c fan and same radiator.

no more drive though with half - 3/4 gauge hot.
 
I tried to find the difference between 6and 8 blade a few months ago. I found a lot of mixed info but one guy on the barracuda owners group site said he has a factory service manaul from 1969 thAt lists the ac car with six blades. My car has air and the old pump had 6 blades. I put an 8 blade on because I couldn't find a 6 blade local in stock. So fAr it runs pretty cool with a 160 tstat. I have a mostly stock 340.
 
My 318 in my 68 cuda had an 8 blade iron water pump. Im rebuilding it with the aluminum 6 blade mopar unit i got from summit. I'll let u know how it works out for me...
 
mopardude318 said:
My 318 in my 68 cuda had an 8 blade iron water pump. Im rebuilding it with the aluminum 6 blade mopar unit i got from summit. I'll let u know how it works out for me...
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yeah.. it would be nice to know how this applys/effects to an 'aluminum head' engine.

kind of a different animal in the heat transfer department.
 
My understanding through the years has been that the factory A/C cars used the 6 impeller pumps and the non/A/C cars used the 8 blade type. The logic on this is that the A/C pumps spin faster because of the smaller diameter pulley so it ends up being the same water flow as a non-A/C setup with a bigger pulley and more blades. Now when you start changing to non-stock gear, it's anybodys guess as to what will work the best. I've seen some 8 impeller systems that cavitated and churned the coolant into a foam. Once they swapped to a 6 impeller, the system worked fine. Either way, use a thermostat! A 180 seems to work the best for me in SoCal. The heater works and the hoses and wiring don't get fried under the hood.
 
cudamark said:
My understanding through the years has been that the factory A/C cars used the 6 impeller pumps and the non/A/C cars used the 8 blade type. The logic on this is that the A/C pumps spin faster because of the smaller diameter pulley so it ends up being the same water flow as a non-A/C setup with a bigger pulley and more blades. Now when you start changing to non-stock gear, it's anybodys guess as to what will work the best. I've seen some 8 impeller systems that cavitated and churned the coolant into a foam. Once they swapped to a 6 impeller, the system worked fine. Either way, use a thermostat! A 180 seems to work the best for me in SoCal. The heater works and the hoses and wiring don't get fried under the hood.
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show me the smaller a/c pulley.
 
1wild&crazyguy said:
show me the smaller a/c pulley.
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Here you go....There were many combinations through the years but these are all off a '73 model 318 so we're comparing apples to apples. The pulleys on the right are the A/C ones and have about a 7 3/8" diameter crank pulley with a 6 1/8" water pump pulley. The non A/C setup on the left has a 6 1/8" crank pulley with a 6 7/8" water pump pulley. This means the A/C water pump is overdriven and the non A/C pump is underdriven. To achieve the same water flow, the A/C pump needs fewer impellers (since it's spinning faster) which is why it has 6 instead of 8. The big blocks used the same idea but different pulleys. This is why it's not a good idea to mix and match between A/C and non A/C pulleys (even if they line up, which is rare). You can get into all kinds of cooling problems.

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