Water Pump Impeller Design - best for high RPM track use

Looking at all angles to help with some overheating on our 85 300zx turbo Lemons car. We have been racing this car for 11 years and overheating hasn't been one of the big issues until recently. I will be focusing on water pumps in this post.

Of the pumps available on RockAuto, there seems to be 3 styles of water pump impellers that the various manufacturers use.

 6 blade with long "paddles" (WJB, US Motor Works):

7 blade with medium paddles (SKP, Nissan OEM discontinued, GMB, Gates, Beck/Arnley):

8 blade with short paddles (Aisin):

And the block where the water pump lives:

This motor lives between 3-6k rpm. The water pump is pullied such that it runs at 7650 when the engine is at 6000 rpm. 

Is there a best design for water pump impellers used on race cars for cavitation prevention, flow, efficiency, etc.

The "shuriken with straight paddles" type of design in general is not a good one, good water pump designs look more like a squirrel cage fan or turbocharger wheel, examples:

The best way to tell which of these 3 "highly budget oriented" designs is best would be with practical testing or CFD analysis, they probably flow different amounts at different RPMs, but an eyeballing from someone with a fluid dynamics education might be the next best thing...from what I can find a larger number of smaller blades is better at resisting cavitation at high RPMs, so for spending a lot of time near redline the Aisin might be best bet. They do tend to engineer things decently so if I just had to go by brand name, the Aisin would be my choice as well...

Which pump design worked for the previous 11 years before the overheating issues started? Did you start turning more rpm and run into the overheating problems or has that remained the same?

Head gasket.

In reply to GameboyRMH :

"highly budget oriented" indeed. As far as I have been able to find, there are no water pumps for this application that have decent looking impellers like you referenced. 

I was leaning toward the Aisin as well based on the name/rep, but that impeller was the only one like that. 

In reply to adam525i :

There are several other issues at play on the overheating (big intercooler blocking flow, no rad ducting, increasing boost, etc) which we are working on as well. 

The last pump that was on the motor was a 7 blade style. I have a spare that is an 8 blade. 

I was looking at getting a new pump for the refreshed engine and noticed the different impeller designs and was surprised how different they are. 

Thought I would ask the hivemind if there are any general rules for picking a water pump based on the different impeller designs. 

In reply to Noddaz :

Yes. We have 2. Sometimes...

It seems like overheating = headgasket in these VG motors. 

This is the OE Nissan part, for what it's worth. When in doubt I would buy whatever's closest to the part design that Nissan threw its hat behind.

In reply to pointofdeparture :

Interesting. That looks like the Aisin one. When I looked up the Nissan part it came up with 21010-02P26 and the only pic I found was like the 7 blade ones above. Looking further, 02P85 is for the 87 and later 300zx. No real difference that I can tell. 

Found out years ago when racing TR7s, that the early 6 vane water pumps were great.  Switched to the later 12 vane pumps and car would overheat.  Think it was due to cavitation from the pump spinning faster.  Later went on the grind off three of the vanes on the 6 vane and the car ran even cooler.

Can you just slow the pump down with different pulleys? RX7's have a huge problem with racing rpm's and stock pumps. Slow the pump down and it has a chance to move coolant.

In reply to nicd :

Aisin made a lot of the factory water pumps in the 80s and 90s. Good chance the Aisin is exactly the same.