Request pros and cons high volume water pump

[Paul Cantin #15830]

Many participants suggested installing a new DeWitt radiator to cure overheat at idle problem-67 300 H.P. Automatic and Air Conditioning.

New radiator and surge tank arriving today

Also ordered a high volume water pump-all to be installed today.

Some have said the high volume pump may not be a good idea.

Looking for suggestions before this mornings installation.

[G B.]

No drawbacks

I can't imagine why someone would think a high volume pump would be a bad idea. I've been using Stewart pumps for the last ten years with no problems or failures.

Maybe they've heard the old wive's tale about water "moving too fast through the radiator to have time to cool". This is a crock from the fifties. Actually, the higher the pump flow, the better the cooling.

[Paul Cantin #15830]

Re: No drawbacks

Gerry-- Thanks for your quick response.

That's exactly what they told me, along with plenty of old drag race stories to "back it up"

[Doug Flaten]

Re: Jerry is Right

Heat transfer is related to mass transfer. If you can move more water or more air across the radiator, you can dissipate more heat. Of course the only downside is the additional horsepower required to move more air or water.

[Tom B.]

Re: A little surprised...

Jerry,

I'm surprised that you can't imagine why someone can't imagine using a high flow system. It's an easily misunderstood concept, of course. At least it is by know-nothing guys like me.

No need to go back through all that heat transfer rig-a-ma-role again. I was shown the error of my ways the first time around. Anyway, I thought we all learned something in the end. Like using high flow water pumps, and leaving thermostats or restrictors in place (instead of recommending that people remove them and go for a drive). Though I have little doubt (now) that a high flow water pump wouldn't help, I (for one) am not always convinced that it's the best way to go. Better flow, if that's the case, is one of the reasons I mentioned the flow restrictor in place of the thermostat to Paul in the first place. TBarr #24014

[Iron Duke NCRS #22045]

Re: Request pros and cons high volume water pump

In a 1992 SAE paper written by GM engineers on the then new LT1 V8, they stated that the coolant pump flow rate was dictacted by cockpit heating requirements at idle in cold weather. The implication here is that the flow rate at higher revs is excess of cooling requirements. High revving racing engine are often equipped with "low flow" impellers, which can increase peak power by two or three percent and help keep the pump out of cavitation. Also production oil pumps can deliver too much oil at very high revs and can get into cavitation, so low flow pumps are the way to go if revs are substanitally raised.

For a production or mildly modified engine, I would stick with the production design or go low flow. With a new DeWitts radiator, your car should have plenty of cooling capacity with the standard impeller.

Duke

[John M.]

Re: Jerry is Right

Doug, the only other possible downside which probably not be aplicable to cars but is a problem in commercial chillers is erosion of the soft tube structure from water velocity which is too great. John Mc Graw

[G B.]

I am soundly rebuked

Please allow me to change my prior testimony.

I can now imagine why someone would not want a high flow pump. These reasons include, but are not limited to: 1) They are concerned about the horsepower it takes to drive the water pump, 2) They intend to keep the engine near its redline for a sustained period and/or they do not idle their cars in very hot weather, and 3) They believe that "water can move through the radiator too fast to have time to cool".

Frankly, I still consider reason #3 to be a crock.

[Bill Becker]

Convert Original BB Pump To High Flow?

Is it possible to rebuild a stock BB pump into a high volume?

Bill Becker

[Dale Pearman]

JERRY IS RIGHT!

It is a crock!

Varoom!

[Chuck S.]

Re: Convert Original BB Pump To High Flow?

Bill,

To increase the flow volume of a centrifugal pump, you would have to increase the impeller height or rotational speed. I suppose you could accomplish higher volume by installing a smaller pulley to increase the speed, but that could increase the bearing and seal loads, causing service-life problems. I doubt that the impeller configuration could be changed enough to make any difference.

Chuck Sangerhausen

[motorman]

Re: Convert Original BB Pump To High Flow?

some late model water pump have a stamped steel water pump impeller. these impellers have a large open space on the back. you can improve the efficiency by pop riveting a brass disk to the back side of the impeller.the older style impeller was cast iron and was solid on the back.

[Chuck S.]

Re: Convert Original BB Pump To High Flow?

Motorman,

You know, I had read some of the NDB threads about the disc being riveted to the impeller, but didn't realize that the newer impellers had an open hole in the back.

Now I see; the open back creates a "recirculation loss", i. e. the flow comes off the impeller outside diameter (high pressure) and some fraction flows back down behind the impeller to re-enter the "eye" of the impeller (low pressure) through the open hole. The flow volume is therefore reduced by that fraction being continuously recirculated. Riveting the disc over the hole eliminates this recirculation loss, and increases the water pump flow by the amount that was being recirculated.

Someone, my engine rebuilder or water pump rebuilder, can't remember which, told me the old cast iron impellers were superior to the stamped steel (didn't explain why). He said to be sure and hang on to my cast iron impeller, cause they weren't making any more.

Chuck Sangerhausen

[motorman]

Re: Convert Original BB Pump To High Flow?

back in the good old days we used to grind every other vane off of the cast iron impellers for use in race cars to prevent cavatation, but now with pulleys that allow you to reduce the speed of the pump you do not have to do it. these new race car engine builders have it made, just open a catalog and get out your visa card!

[Everett "Heat Transfer" Ogilvie]

Oh you guys...

Don't get me started on heat transfer again. Heat transfer has a rate. A rate implies that with more time, more heat is transferred. All the arguments in the world will not dispel the physics nor the units. Put your finger on something hot. Try just touching it quickly compared to leaving it there. I wonder which one transferred more total heat. If the hot water in your radiator was an open system whereby fresh cold water was always returned to the block then more water flow would rule. The water would be transferring the heat out of the system mostly by itself. But your car's system returns relatively hot water to the block. The hotter that water the less effective the cooling in the closed system. Think about if you could fill your radiator with hot water just sitting in the radiator. Turn on an electric fan. Feel the temp of the air on the other side of the radiator. At first it is hot b/c the moving air (forced convection) is removing lots of heat from the system. After a while the air temp becomes ambient. That is because all the heat is now out of the system. That did NOT happen instantly. It took time. If your radiator is not brand new and at its peak efficiency, because it is filled with scale which is an insulator, then the time the hot water spends in the radiator can become critical because the rate of heat transfer from the water to the air is impacted. If you don't get the heat out of the water while it is in the radiator, where do you think that heat goes... maybe back into the block? Now fire away guys...