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69NovaSS said:
ya I've heard the same thing...but it was only about 20 degrees...whatever it is there is suposedly a difference between the two locations :)
Well...this would mean when on the highway, I am truely running only 180-195 instead of 200-215 (head reading).


The problem is when I get off the highway. The sender reads 210, 215, 220...i pull in a gas station shut it off and it quickly rises to 230-240 and pukes a little antifreeze out the overflow. (again...this is all on the head reading).

Which would lead me to believe the temps are a true (*intake reading), 185-190 on the highway....and creeps to 200, 205, 210, and when I shut it off it quickly jumps to 220, 230+ and it pukes a little antifreeze.

My sender is not insulated either from the header. humm...Still doesn't change the fact that it gets hot enough to puke antifreeze after shutting it down from a highway blast. I've also heard timing too retarded would make it run hot constantly. Is this true?

I am going over to a friends house tonight to get to the bottom of this. could be timing for all I know.
 

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FunkyNova66 said:
Well...this would mean when on the highway, I am truely running only 180-195 instead of 200-215 (head reading).


The problem is when I get off the highway. The sender reads 210, 215, 220...i pull in a gas station shut it off and it quickly rises to 230-240 and pukes a little antifreeze out the overflow. (again...this is all on the head reading).

Which would lead me to believe the temps are a true (*intake reading), 185-190 on the highway....and creeps to 200, 205, 210, and when I shut it off it quickly jumps to 220, 230+ and it pukes a little antifreeze.

My sender is not insulated either from the header. humm...Still doesn't change the fact that it gets hot enough to puke antifreeze after shutting it down from a highway blast. I've also heard timing too retarded would make it run hot constantly. Is this true?

I am going over to a friends house tonight to get to the bottom of this. could be timing for all I know.

yes the timing can cause this so I would check that...

The factory used to put the sending unit in the head (BTW that is where mine is and not insulated from the headers either and I have no issues with it) and they didnt have any problems....so its really not the location that is the problem...I would check your timing, possibly change out your lower hose and possibly put in a high flow thermostat as some easy fixes for this...
 

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The cylinder head is where the fire is. The intake is where the cool water from radiator is returning to the engine from.
I have been told that running block filler in an engine 2/3 or even 3/4 up in the block isn't that big of a deal. All the heat from a engine starts in the combustion chamber, it would stand to reason that the head would be the hottest part of the engine. On a BBC the temp sender goes between the exhaust ports, that should be the hottest side of the head, the sender on the intake is in the inlet side right beside the thermostat. That should be the coolest point in the engine I would think.
 

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Nova_Guy said:
The intake is where the cool water from radiator is returning to the engine from.
Actually...the thermastat opens and all the hot water comes out of the motor into the top of the radiator. The hot water runs down the radiator, cools off and returns (cool) into the block via the lower radiator hose. So the coolest part of an engine would be the water pump inlet. I think...:eek: Someone correct me if I am wrong....

But I would still agree with ya Nova_Guy the water in the head (where combustion takes place around it) is much hotter than the water at the top of the intake.
 

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This is my last two cents on this one

No I never said anything about a cavitating pump moving more coolant than a non cavitating one.... What I did say is that if you look at the links that you posted from arrowhead radiator, they say that it is possible for a pump to be moving water fast enough to make it cavitate and foam up the coolant, therefore you have to slow it down.

All I will say is I had a new edelbrock aluminum pump, and a 180 degree thermostat on the car. I put the small restrictor in and it dropped a little, the guy at Be Cool told me to try a stock water pump and I put a $14.00 Autozone pump on there and the car went from running 220-225 on the highway to a steady 180.

I sold the water pump to a buddy for 20 bucks and it works great on his camaro...go figure.

I will also say this, I have a .060 over 400 small block with a mega ported set of iron heads and a .674 lift solid roller in my street car, with a stock water pump and a stock camaro 3 core radiator and it doesn't ever get over 170 degrees. So, I guess I may not be the most gifted braniac when it comes to the laws of physics and heat transfer, but I think I know what makes an engine not overheat.

I have put pics of my street motor on the photobucket acct below, just in case anyone would like to see that there are 900+ horsepower street cars running around. The nitrous kit in case anyone wants to know at the time was a 350 hp fogger. It now has a 400 hp dual stage plate.

David
 

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FunkyNova66 said:
Actually...the thermastat opens and all the hot water comes out of the motor into the top of the radiator. The hot water runs down the radiator, cools off and returns (cool) into the block via the lower radiator hose. So the coolest part of an engine would be the water pump inlet. I think...:eek: Someone correct me if I am wrong....
You are correct in your thinking. I am always surprised at how may people have no idea what direction the water flow is in these old engines. Now some of the late stuff has reverse flow, through the heads and out the block but not these old ones.
 

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Discussion Starter #27
I agree with you.. I think the coolant is moving to fast through the system and cant cool off.. It can pickup heat but cant transfer the heat away in the radaitor.

I have no vacuum advance, mechanical advance, etc because the Electornic Control Modual, that and the Electornic Spark Control Modual, takes care of the timing. I have an initial timing of 10 degrees which is about 4 degrees above what Chevrolet says you should set the timing.


69NovaSS said:
normally speaking if a car can sit all day idling but over heats when driving down the road it is a coolant flow issue....and normally it is not enough flow that is causing the problem...conversely if it sits in the driveway and overheats but can drive down the road and not over heat normally speaking that is an airflow issue that is causing the problem...and you need to look at your shroud, fan, and how far your fan is set into your shroud, etc, etc.....

BTW you said you dont have vacuum advance but your initial timing is only 10 degrees advanced....that sounds really low cause normally you have to make up for the lack of vacuum advance...so 20 or so is normally a ball park figure.....BTW retarded timming can cause overheating...so possibly that is a place to look too.....just my 2cents:)
 

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Mike Goble said:
Next weeks topic will be the Mpemba effect.
Is that the effect where proven theory is ignored because that theory doesn't comply with observed outcome, so the proven theory and thousands of people using it must be wrong? :D
 

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NovatoriusRex said:
Is that the effect where proven theory is ignored because that theory doesn't comply with observed outcome, so the proven theory and thousands of people using it must be wrong? :D
No, the Mpemba effect is the observation that, in some specific circumstances, hotter water freezes faster than colder water.

Mitchc said:
I agree with you.. I think the coolant is moving to fast through the system and cant cool off.. It can pickup heat but cant transfer the heat away in the radaitor.
How slow should it go? If I stop the pump will the system work better? What equation describes the 'knee' in the cooling curve?

If my radiator loses half its heat energy every minute, how much heat does it lose in 2 minutes if I leave the same water in there? It loses 50% in the first minute then 50% of the remaining 50% in the second minute for a 75% loss. If I replace the water at the end of the first minute with a new batch of hot water, I will lose 50% in the first minute and 50% in the second minute, a total of 100% of the original heat energy and an increase in efficiency of 33%.

This physics stuff is pretty interesting...
 

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What a discussion!

I have been reading this discussion for a couple days now and I guess as one more "expert" I"ll add my 2 cents worth. As a chemical Engineer I have some experience with heat transfer and pump cavitation. The note at the start of this tread describes pump cavitation as the cause of the problem pretty clearly. At idle (low RPM) the pump is moving coolant through the system and keeping things cool. As the RMP's increase the the high volume pump is cavitating and flow stops! Therefore the engine heats up and if you add more load at high RMP with the AC it heats up even more. It is heating up because the coolant has stopped flowing not because it is moving too fast though the radiator. If it is moving too fast throught the radiator it is also moving fast throught the block so it isn't as hot and doesn't need as much cooling in the radiator. Cavitation is occurring because the high volume pump cannot pull in coolant fast enough. The suction pressure becomes too low and the pump stops feeding. Therefore the coolant stops flowing. It is basically a closed system (short of the little overflow into the expansion tank) so if the pump cavitates, the flow stops everywhere. In the block and the radiator. Not sure why the suction pressure is getting so low. It indicates the supply hose, radiator and or thermostat are too restrictive for that high flow. The thermostat is the most likely. The pump can create the pressure to circulate the water only as long as the inlet side of the pump is flooded. That is how the centrifical pumps works. It sounds like the thermostat is just too restrictive for the flow the pump is trying to generate at the higher rpm's. It sound to me that the standard pump and a good clean radiator should take care of this problem.

With the electirc fan it is only using the 16" circular area it covers on the fan when the car is stopped but you use the entire radiator as you are moving it is fairly typical for motor temp to go up as you roll off the highway and shut down the motor, especially if the you have a sending unit in the head versus the intake.

Mike I'm old and slow Mpemba?
 

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There is no way that the coolant is moving to fast to cause overheating. A coolant system uses forced convection to cool. Forced convection happens when motion of the fluid is imposed externally (such as by a pump or fan).
Now, the faster heat is transfered (by forced convection) from an object the cooler it gets and the cooler the fluid stays. This creates a lower operating temp. If the fluid were to be moving slower it would get warmer thus impairing cooling and making the system run warmer. Thats why a car with a good cooling system always runs warmer in stop and go and not on the freeway. You are curculating less fluid at lower RPM speeds and no air flow to dispate the heat off the radiator causing insufficiant heat transfer. The heat transfer is greater when cooler fluid is moving over the surface, and for the fluid to remain cooler it must move over the surface faster, creating less heat obsorbtion while promoting heat transfer. This is good. Not to mention that the cooler the fluid in comparssion to the object creates greater heat absorbtion.

The radiator on your car is like a giant heat sink. Its only job is to soak up heat inside and bring it to the surface. A radiator does not cool the coolant at all. It absorbs heat. The fluid getting cooler is just a side affect. The point of a radiator fan is not to cool the fluid but to cool the surface of the radiator so there is a greater heat transfer. Once again creating a cooling side affect on the fluid. Also, the cooler the fluid the less work your radiator has to do. Obviously a aluminum radiator is better because aluminum absorbs and dispates heat quicker than a conventional radiator.

Now cavitation is a completley diffrent story. I don't personally see how your system could be causing cavitation at higher RPMs, unless there is a pressure leak somewhere, that is causing a low suction rate. The pressure in the system also helps suck fluid into the block as well, it assists the pump and prevents cavitation. The pressure your pump produces to push coolant is directly perportional to the pressure that it sucks(in a closed system). If there is a disruption in the system ( like a pressure leak or a restrictionaka kinked or smashed hose) it will have trouble creating the vacuum and coolant that is needed to feed the pump. Cavitation will not happen if the supply is always avalible. Just take your own heart for example. Does it cavitate when you go for a jog and your heart rate rises. NO. not unless there is a blockage or a restristion. So how would a pump cause cavitation at higher RPM speeds? Unless the inlet pressure is less than the output pressure. Also, could be your exhaust. the longer the heat sits in the exhaust chamber the more heat is transfered to your engine.
So thats all I have to say about that.:D

So IMHO you should check all your hoses and radiator cap, pressure check your system, put headers on if you don't got' em, check your timing, and burp the system and that should do it. Also, If your car is a darker color it will also create greater under hood temp.:)

I hope this helps:D
 

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Yes, that should be good. It will really help to put the sending unit on the intake. You want get a high reading. Also burp your system that will help too. Good luck and let us know how it goes.
 

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Being a lifetime car guy, working as a mechanic, and 26 years as a firefighter, I have a lot of ideas on the cooling and cavitation issues. But...............based on all of the prior e-mails, I'll keep it simple. Most cooling problems are caused by basic/common issues that really haven't changed since the first water cooled motor was invented.

That said, I have a blown pro-street Nova that I race and also drive on the street. 13# boost, Griffin radiator, SPAL electric fan. No problems, and it gets driven on 100 degree days.

Mike: Ain't physics great!!
 

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nova656567 said:
Being a lifetime car guy, working as a mechanic, and 26 years as a firefighter, I have a lot of ideas on the cooling and cavitation issues. But...............based on all of the prior e-mails, I'll keep it simple. Most cooling problems are caused by basic/common issues that really haven't changed since the first water cooled motor was invented.

That said, I have a blown pro-street Nova that I race and also drive on the street. 13# boost, Griffin radiator, SPAL electric fan. No problems, and it gets driven on 100 degree days.

Mike: Ain't physics great!!
So what are you saying???:rolleyes: ;) :D
 
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