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I have noticed something recently. The billet crank pulley I installed when I rebuilt my motor is smaller than the factory pulley. Probably 1.5" smaller. than the factory one. The car only gets hot in 80+ deg weather in heavy traffic. On occastions, it will creep to about 200, 205, 210, 215....which I know is not bad but I don't like it. The rest of the time it sits at 190-195 deg.

Can you overdrive your cooling system too much and prevent it from cooling properly in traffic? Somebody I know had noticed how small my crank pulley was and asked me if I had overheating issues. He seemed to think the crank pulley was too small. So I came home, measured the current pulley and sure enough it was considerably smaller than the factory pulley 1.5" smaller. Is overdriving a cooling system possible and what would be characteristic if this was the case?

I have a hard time believing my brand new factory 4-core radiator is too small for my application. I'd hate to buy an expensive radiator set up only to find out I could have put the factory pulley back on to fix the problem.

I'm just curious to know if anyone has ever heard or experienced this.

Dave
 

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More flow equals more cooling, that's how the physics works on both sides of the radiator. What is the ratio of the pulleys you have on your car compared to the stock ratio? This will determine the pump speed compared to the engine speed.
 

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More flow equals more cooling, that's how the physics works on both sides of the radiator. What is the ratio of the pulleys you have on your car compared to the stock ratio? This will determine the pump speed compared to the engine speed.
  1. The factory water pump pulley is the same size a the billet one I bought..6" or so.
  2. The alternater pulley is stock size also
  3. The billet crank pulley is 1.5" smaller (6.5" )than the factory pulley (8").
Wouldn't this mean the crank pulley is underdriving the rest of the system like veno suggested?

Thanks guys for putting this into perspective for me. Keep the comments coming. I think I am on to something.

Dave
 

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What do you mean by ratio? I went from 6 3/4 crank to 7" crank and 7" water pump pulley to 5 1/4" pulley . This combo is March's cooling ratio? Do you agree?
 

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If the pump pulley is 6" in diameter and the crank pulley is 6.5" in diameter, the pump is technically being overdriven as it is rotating faster than the engine. Compared to the original configuration of an 8" crank pulley, the pump is rotating about 80% as fast.

What do you mean by ratio? I went from 6 3/4 crank to 7" crank and 7" water pump pulley to 5 1/4" pulley . This combo is March's cooling ratio? Do you agree?
The ratio is crank/pump. 7/5.25= 1.333, which incidentally is exactly the same as 8/6, the stock pulley system described by Funky.
 

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Two things here, if the water pump turns at to high a rate then cavitation can occur and water will be stalled. BILL Jenkins also said that if the water passes through the block to fast then it does not spend enough time in dwell to effectively remove the heat for the engine.

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:The car only gets hot in 80+ deg weather in heavy traffic.

Like nascar, Drafting cuts wind and pulls the other racer along, but spent to much time drafting and he over heats be cause he is in a low pressure area and no air circulation.

you may not have a water circulation problem as much as a air flow problem. just a thought.



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Two things here, if the water pump turns at to high a rate then cavitation can occur and water will be stalled. BILL Jenkins also said that if the water passes through the block to fast then it does not spend enough time in dwell to effectively remove the heat for the engine.

Quote
:The car only gets hot in 80+ deg weather in heavy traffic.

Like nascar, Drafting cuts wind and pulls the other racer along, but spent to much time drafting and he over heats be cause he is in a low pressure area and no air circulation.

you may not have a water circulation problem as much as a air flow problem. just a thought.
You believe if the air flow slows through the radiator less heat is transferred? If you subscribe to the Bill Jenkins theory of water flow, why would you not think that leaving the air in the radiator longer would produce the same effect? Maybe the air is going through the radiator so fast it doesn't pick up any heat.
 

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You believe if the air flow slows through the radiator less heat is transferred? If you subscribe to the Bill Jenkins theory of water flow, why would you not think that leaving the air in the radiator longer would produce the same effect? Maybe the air is going through the radiator so fast it doesn't pick up any heat.
1:You believe if the air flow slows through the radiator less heat is transferred?
1a: yes (see #3a:)

2: If you subscribe to the Bill Jenkins theory of water flow, why would you not think that leaving the air in the radiator longer would produce the same effect?
2a: It is saturation effect in both cases, fast water= low saturation of of heat in the water, slow air movement = max saturation effect but not enough air or media to remove latent heat or excessive amounts.

3:Maybe the air is going through the radiator so fast it doesn't pick up any heat?
3a: when dealing with water to air heat exchangers the more air movement through the heat exchanger the better the cooling effect. by moving a large volume of air through small orifices (radiator fins or raidation dispersion fins) you archive a low pressure area behind the radiator there by raising velocity through the orifices. Increassing the cooling affect.



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I used to have a March underdriven pulley on my El Camino. Never could keep the thing cool no matter what I tried until I put the stock pulley back on and then it worked great again. I then sold the pulley on eBay for dirt cheap just to get rid of it.
 

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2a: It is saturation effect in both cases, fast water= low saturation of of heat in the water, slow air movement = max saturation effect but not enough air or media to remove latent heat or excessive amounts.
I'm still at a loss as to why you say air and water behave differently, i.e. water has to flow slowly in low volumes to remove heat from the engine block while air has to move rapidly in high volumes to remove heat from the radiator. The actuality is that water absorbs heat more rapidly when it is colder and at a slower rate as it approaches its pressure corrected vapor point. Flowing slowly through the engine will reduce the ability of the water to absorb heat and increase the incidence of nucleate boiling at the hot spots.
3a: when dealing with water to air heat exchangers the more air movement through the heat exchanger the better the cooling effect. by moving a large volume of air through small orifices (radiator fins or raidation dispersion fins) you archive a low pressure area behind the radiator there by raising velocity through the orifices. Increassing the cooling affect.
The velocity is just a secondary effect, you can't flow more mass through a fixed orifice without increasing the velocity as Bernoulli discovered. In a typical automotive cooling system the temperature differential between the cooling/cooled mediums is the only factor that governs the rate of heat exchange. All else is pretty constant, like the area of the radiator and the area of the engine block, the heat capacity of the coolant and the air density (unless you make a significant change in altitude). The only way to control the rate of heat exchange is to vary the flow of coolant and/or cooling air to control the average temperature differential between the radiator and the cooling air. More flow of either coolant or cooling air will result in a higher rate of heat exchange. This is why a thermostat opens up to increase the flow of coolant when the engine gets hot and electric fans have thermostatic switches that increase the flow of air at higher temperatures.
 

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Alright guys...Let's make this simple.

Should I change the small lower pulley back to the large stock pulley?

YES or NO. (please choose one answer).:D


PRO....thanks for sharing your under drive experience. I think my pulley will be on ebay soon enough.:D
YES.... only to see if your temps drop. if they do....... your conclusions are the most important. not mine.



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