Hey guys, I have a couple of spare parts... was wondering what (in your opinion) is technically a better design between these two water pumps.

They are both for Iron Dukes, same year range... the top one has a closed impeller, and the bottom one has an open impeller. Both are cast... just curious in your opinion, which one would be more efficient and flow more water? I've already gone with one that has the design from the top (simply because it already had the pulley pressed on it)... but just curious for future reference...

quote Originally posted by 82-T/A [At Work]: ...just curious in your opinion, which one would be more efficient and flow more water?

The impellor blades are basically the same. I'd say it's six of one, a half-dozen of the other.

Todd it's really the plastic or stamped metal ones that you want to stay away from. sleek

Thanks guys, I definitely learned my lesson on the plastic impellers. It's one of the reasons I had to rebuild the motor in my V6 Fiero back in 2000. I had the Coltec Industries one... it basically separated from the shaft and stopped pumping. It was crazy.

But I'm just curious if you had to hazard a guess. The one with the open veins looks like it would be more efficient, however, it's creating a passage where the coolant (in my opinion) would have less force since some of the coolant could escape through the back into one of the other openings. That was my thought, but just pure curiosity from a performance / efficiency perspective. Granted, I realize this is an Iron Duke... but if you built up a SuperDuty-4, which one would you run?

The tighter the clearance between the impeller and the housing, and the larger the impeller blades, the more water it will flow for a given RPM.

The impeller with the backing plate would only have 1 set of clearances, but the impeller blade is shorter by the thickness of the backing plate.
The impeller without the backing plate has 2 sets of clearances, but the height of the impeller blades will be higher.

So like everything it will come down to details how much clearance each design has.

On an iron duke that only makes 100 hp, it doesn't really matter... you are not making any significant heat.

quote Originally posted by fieroguru: The tighter the clearance between the impeller and the housing, and the larger the impeller blades, the more water it will flow for a given RPM. The impeller with the backing plate would only have 1 set of clearances, but the impeller blade is shorter by the thickness of the backing plate. The impeller without the backing plate has 2 sets of clearances, but the height of the impeller blades will be higher. So like everything it will come down to details how much clearance each design has. On an iron duke that only makes 100 hp, it doesn't really matter... you are not making any significant heat.

I have it on good authority that this adds about 20 horsepower, the little holes I mean. Haha... I know, it's just my curiosity. I would love to know which one is more efficient, even if by 0.000001%.

They both appear to have (eye-ball test) identical clearance to the water pump housing block.

quote Originally posted by 82-T/A [At Work]: I have it on good authority that this adds about 20 horsepower, the little holes I mean. Haha... I know, it's just my curiosity. I would love to know which one is more efficient, even if by 0.000001%. They both appear to have (eye-ball test) identical clearance to the water pump housing block.

If your desire to know is greater than the effort to know... install both in a housing off the engine, run each at a constant RPM and measure the actual water flow over time.

Man I missed this earlier, Guru spot on in my opinion.

This open wheel impeller has a face that it can't touch for obvious reasons, the larger the gap between the 2 well the less fluid you get through.

quote Originally posted by fieroguru: If your desire to know is greater than the effort to know... install both in a housing off the engine, run each at a constant RPM and measure the actual water flow over time.

I am so tempted... though, if I go through all the effort, no one in this world will benefit from such useless information about Iron Duke water pumps. Hahah...

I think what I wonder most is why these two impellers were designed this way. Was the intent for one of them to be better... or was the different one (open impeller) just made cheaper because it uses less material?

Todd, besides it being a water pump, do you know what kind of pump it is ?

I do , from my "drill baby drill" experience. That is a Centrifugal pump. All car water pumps are of centrifugal design.

Call Knighten Industries. 830-816-5200 is their San Antonio location. Message them if you wish. The San Antonio location may not have the physics knowledge but they will get you answers.

Did you know that there actually are centrifugal beer pumps ?

[This message has been edited by cliffw (edited 01-21-2025).]

Thinking about it, would you rather swim underwater barefoot, or with scuba fins.

Perhaps in this case, size matters. Impeller size.