'72 big block water pump question

[Tom L.]

This past winter I did some work to my car. had the heads done, correct fan, correct water pump. Once summer came it ran warmer than before the work was done. It is discussed further in a thread I posted earlier in the summer. Read further if you like:

https://www.forums.ncrs.org/showthre...running-warmer

Recently, in cooler weather below 60*, I noticed that it ran as cool as before except in traffic. Even in that cool weather the temp crept up but not nealy as much as in warmer weather. I eliminated the fan as the cause since I put the old one back on to see if that was the problem, it's still on there. I had read that water pumps used a cast impeller. I was able to find a pic in the archives. There was also discussion indicating that a corroded impeller can lead to problems as well as a cast impeller replaced with a stamped steel one.

I decided to take the back cover off of the old pump, a high flow pump made by "Flow-Kooler". The casting doesn't look special but there is one modification to the impeller. It uses a stamped impeller with a sheet-metal disk rivited to the back of it. It appears as if they were mimicing the cast impeller by putting the disk on. After seeing the cast impellers and this one I thought perhaps the impeller itself may be the culprit.

So my question is this, what is the likelyhood of the rebuilt original pump having a badly corroded impeller OR being replaced with a stamped steel one without the modification that my aftermarket pump had??

[Edward J.]

Re: '72 big block water pump question

Lynn,That plate is likely the reason they call the pump a high flow, The plate aids in the flow of anti freeze.

The not likely your pump would have a impeller that corroded since most of the rebuilders use the stamped steel impeller if the old impeller is beyond using. when the rebuilders use the new bearing for the water pump its my understanding that to use the factory impeller it will require some machining.I would think that the only way to tell which impeller you have is is to remove your rebuilt pump and inspect.

[Joe L.]

Re: '72 big block water pump question

This past winter I did some work to my car. had the heads done, correct fan, correct water pump. Once summer came it ran warmer than before the work was done. It is discussed further in a thread I posted earlier in the summer. Read further if you like:

https://www.forums.ncrs.org/showthre...running-warmer

Recently, in cooler weather below 60*, I noticed that it ran as cool as before except in traffic. Even in that cool weather the temp crept up but not nealy as much as in warmer weather. I eliminated the fan as the cause since I put the old one back on to see if that was the problem, it's still on there. I had read that water pumps used a cast impeller. I was able to find a pic in the archives. There was also discussion indicating that a corroded impeller can lead to problems as well as a cast impeller replaced with a stamped steel one.

I decided to take the back cover off of the old pump, a high flow pump made by "Flow-Kooler". The casting doesn't look special but there is one modification to the impeller. It uses a stamped impeller with a sheet-metal disk rivited to the back of it. It appears as if they were mimicing the cast impeller by putting the disk on. After seeing the cast impellers and this one I thought perhaps the impeller itself may be the culprit.

So my question is this, what is the likelyhood of the rebuilt original pump having a badly corroded impeller OR being replaced with a stamped steel one without the modification that my aftermarket pump had??

Lynn------


I doubt that the waterpump is the source of your problem, if there is, indeed, a real problem.

The Flowkooler impeller back-plate makes the stamped steel impeller about as efficient as the cast iron impeller. They used to sell these backplates separately in a kit with rivets and instructions. In fact, I bought one and have it around here somewhere since I never used it. I don't know if they still sell them.

As has been mentioned, the only way to know what impeller is installed in your pump is to remove it and open it up. However, you may be able to remove the radiator hose and "peer in" to see if it's a stamped steel or cast impeller. You won't be able to assess the condition of the impeller, though.

[Tom L.]

Re: '72 big block water pump question

Thanks for the responses, I'm going continue beating this horse to death so my apologies in advance. I do get the fact that I'd have to remove the pump to find out which impeller I have, I was really trying to see what the difference in performance would be so here it goes again.

Edward, you suggest that rebuilders would have to machine the new bearing to accept the cast impeller. I'd guess that extra cost would motivate rebuilders to discard the cast impeller and replace it with an inexpensive stamped steel one. Is that correct??

Joe, you seem to feel that the stamped steel impeller with the disk installed makes it "...about as efficient as the cast iron impeller."

With these thoughts in mind, would anyone be willing to estimate how much more efficient the cast impeller is over the plain stamped steel one? 5%, 10%, 20%?

Thanks for the help, seems I'm perseverating over this a bit much.

[Dick W.]

[Edward J.]

Re: '72 big block water pump question

Lynn, Its the cast impeller impeller that gets machined not the bearing. The stamped impeller that the re-builders use is like the high flow one less the flat plate attached to the back of the high flow pump.

As far as the flow difference, I truly think that the only way to find out the efficiency of the cast and the high flow pump would be to bench flow test them.

[Joe L.]

Re: '72 big block water pump question

Thanks for the responses, I'm going continue beating this horse to death so my apologies in advance. I do get the fact that I'd have to remove the pump to find out which impeller I have, I was really trying to see what the difference in performance would be so here it goes again.

Edward, you suggest that rebuilders would have to machine the new bearing to accept the cast impeller. I'd guess that extra cost would motivate rebuilders to discard the cast impeller and replace it with an inexpensive stamped steel one. Is that correct??

Joe, you seem to feel that the stamped steel impeller with the disk installed makes it "...about as efficient as the cast iron impeller."

With these thoughts in mind, would anyone be willing to estimate how much more efficient the cast impeller is over the plain stamped steel one? 5%, 10%, 20%?

Thanks for the help, seems I'm perseverating over this a bit much.

Lynn-----


I don't know the efficiency difference between he plain stamped steel and the cast. However, keep in mind that more flow is not necessarily a better thing, at least beyond a certain point. There is such a thing as having too great a flow rate. This moves coolant faster through the radiator than the radiator can dissipate the heat. At this point, the higher flow actually causes overheating.

[Dick W.]

Re: '72 big block water pump question

Lynn-----


I don't know the efficiency difference between he plain stamped steel and the cast. However, keep in mind that more flow is not necessarily a better thing, at least beyond a certain point. There is such a thing as having too great a flow rate. This moves coolant faster through the radiator than the radiator can dissipate the heat. At this point, the higher flow actually causes overheating.

That is the reason we cut every other impeller of the water pumps on flathead F**D's when we raced them. Too much water flow.