Waterpump questions with new radiator

Vanspeed

Vanspeed

Well-known member
I think I am going to have to re-core the radiator in my 29 CCPU, it does not leak but it is obvious that a fan broke and did some damage. It is all brazed up from back in the day. I just installed a leakless kit in my original pump housing and there was a note inside saying that you need to trim the impellers if running a new radiator? Is this true or is it not?
 
Check the fit of the pump without a gasket. If the impellers do not rub the inside of the head when the pump is bolted tightly in place, then they are fine. If they do hit it, trim them so they just clear. Then the gasket will provide enough clearance when it is installed. Be careful when initially tightening the pump that you do not break it. Check the impellers frequently as you tighten the pump to insure they are still clearing the head. I cannot imagine why you would trim the impellers on a new core.
 
Generally speaking, a new core would flow more volume than an old "stopped up" core, ...thus since trimming impellers to limit the volume of water it would move doesn't really sound like prudent advice, does it? Is this a professionally written note or a hand written one? Also, who is selling this kit??
 
I saw the same information on my rebuild kit a few years ago. I trimmed the blades down for use with a boiled and rodded radiator. I wasn't happy with the reduced water flow as the Rexaco gauge consistently showed a 20 degree higher basal temperature than the pre-rebuild system.

I went with a leak less pump, and found the summer run temperature ran less than 160 degrees with the full eared impeller. You might want to look at a thermostat for winter runs because of the full flow of the system.
 
BRENT in 10-uh-C said:
Generally speaking, a new core would flow more volume than an old "stopped up" core, ...thus since trimming impellers to limit the volume of water it would move doesn't really sound like prudent advice, does it? Is this a professionally written note or a hand written one? Also, who is selling this kit??
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More water flow lower temps, possibility of never reaching 160 degrees?
 
I realize that the Model A water flow system is not EXACTLY like those of newer cars, but I can make a case for SLOWING water flow thru the radiator.

I have had several experiences where it was determimned that an increase in water temperature was caused by water flowing too fast thru the radiator, not allowing enough time for the heat to fully dissipate thru the core.

In my case, I made adjustments by changing the angle of the fan blades to slow down air flow until the correct water temperature was reached.

It would be my thinking that the water pump folks were smart enough to have been exposed to this process and knowing that most Model A folks think more fan is better, opted to suggest this method.

It might seem that the root problem would tend to be in the lack of understanding regarding thermal dynamics. The radiator and water pump folks have surely come to their own conclusion regarding the change in temperature required versus the amount of time it takes to achieve that temperature change.

Additionnaly, the only time I tried a four blade fan on my Tudor the water temperature went up a noticeable amount. I was using an original early Ford four blade fan and what I ended up doing was cutting off the prutruding sections of the front blade. This remaining section of the front blade acts as a safety plate for the rear blade. I have had this arraingement in place for 7-years so far.

Just a thought.
 
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I follow your reasoning Will but wouldn't the prudent way be to just install some sort of a restriction such as a thermostat if the overheating issues are due to water transfering too fast? I first remember this talk about trimming impellars during the late 60s/early 70s back in Texas when cars would push out water however the biggest reason I remember why it was being done is because there were many guys who had purchased those cheap 2 core radiators like JC Whitney sold that just didn't seem to flow a lot of water.

Also, as I sat and pondered what Will said, could another part of the 'root problem' be that folks do not understand how they can correct low engine temps just by adjusting the GAV when they are using an efficient radiator?
 
Vanspeed said:
I think I am going to have to re-core the radiator in my 29 CCPU, it does not leak but it is obvious that a fan broke and did some damage. It is all brazed up from back in the day. I just installed a leakless kit in my original pump housing and there was a note inside saying that you need to trim the impellers if running a new radiator? Is this true or is it not?
Click to expand...

Maybe because some of the cheap radiators would not flow as much as the pump would put out. Which causes the water to run out the over flow.
If you have that problem put in a thermostat. I would not trim the impeller, and I would not buy the cheap radiator.
 
If you slow the flow thru the radiator by installing a restriction, it will also slow the water flow thru the block and add more heat to the water. I would think that the first issue would be to get the heat out out of the block, then work on dissipating the heat before it returns to the block.
 
I got the kit from Snyder's. It is a typed out note showing how to trim the impellers. It says that you need to slow the water movement with the new radiator.
 
RockHillWill said:
If you slow the flow thru the radiator by installing a restriction, it will also slow the water flow thru the block and add more heat to the water.
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Then, conversly, if the flow is fast thru the radiator, less heat will be added by the block. Sounds like a Catch-22. Except it just doesn't work that way. It's a balance that is upset by a new radiators flow design or blockage in an old radiator.

The water going into the radiator is decreased with both methods. Less water pumped is the same as less water allowed due to a restriction, except the restriction causes a very slight increase in engine load which adds slightly more heat.

The purpose of trimming the impellers is to prevent the pump from moving more water than can flow through the radiator (see BRENT in 10-uh-C post # 10). I also read that the water will collect in the top tank, because modern cores don't flow the same as an unpressurized older system, and it will go out the overflow (no pressure cap) until the car overheats. I was having that problem and cured it by taking my radiator to a shop to get it rodded. They said I should just let them clean it, so as to not open a soldering can of worms. I agreed, they cleaned, it keeps its water now.
 
Maybe I should try and locate a good used original. I could always run the one that is on it but is it nasty looking.
 
BRENT in 10-uh-C said:
Generally speaking, a new core would flow more volume than an old "stopped up" core, ...thus since trimming impellers to limit the volume of water it would move doesn't really sound like prudent advice, does it? Is this a professionally written note or a hand written one? Also, who is selling this kit??
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Brent,
I have the instructions from pump #A-8502-A/B sold by Snyder's.

The reason given for the grinding of the impellers is :
"Repo radiators are more efficient because they have smaller diameter tubes to disperse the heat. Consequently they can not handle the same flow rate as oringinal radiators. If you don't file or grind the impeller, and you do have a repo radiator, your pump will pump more coolant into the top tank of the radiator than it can handle. There will be no place for the coolant to go than out the overflow".
 
Thanks for posting that Silvertop as I cannot seem to find my original sheet that came with the pump parts. In regards to fixing the original radiator, I do not see how you could make it look good again as there is about a 6 inch half moon of destroyed tubes that was caused by the original fan breaking. It is all brazed up now but I know the capacity is not the same as it was originally because of all the tubes that are now closed off.
 
Vanspeed said:
Thanks for posting that Silvertop as I cannot seem to find my original sheet that came with the pump parts. In regards to fixing the original radiator, I do not see how you could make it look good again as there is about a 6 inch half moon of destroyed tubes that was caused by the original fan breaking. It is all brazed up now but I know the capacity is not the same as it was originally because of all the tubes that are now closed off.
Click to expand...

Might have to buy a new core from Berg's radiator in IL. Save your tanks and frame to use on the new core.
 
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