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Old 02-15-2020, 06:10 AM
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Default Thermostat or not

I have a 1966 GTO with a Champion radiator ( not the fanciest, I know ) and at speed say 70mph on a 110 degree day, I'm in Australia, the temperature will get to 200 degree measured at the intake, too hot for me. Right now I only have the body of a Thermostat installed, I have a large Aluminium Clutch fan out of 1974 Firebird and two electric puller fans and two electric pusher fans ( see pictures attached ). I have a cast impeller and I have done the clearance thing. The engine is a 400 stroked to 461 with 30 thou. bored out, Butler Kit with stock heads. Is the water travelling too fast through the radiator? will a complete working thermostat be enough to slow it down? or should I use a reducer? What do you guys think?
Cheers.
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  #2  
Old 02-15-2020, 07:43 AM
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I would think you should have a 180° thermostat AND a fan shroud to get it up to temp and maximize air flow to get it in the ballpark.

Proper cast curved impeller and curved plates to match would also be highly recommended.

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Old 02-15-2020, 09:15 AM
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Here is what I would do... remove the electric fans and install a properly fitted shroud for the mechanical fan and a 160 or 180 thermostat. Very important on the properly fitted shroud, fan blade should be half in/half out. Now see where you are at cooling the car.

Problem with all your electric fans is they will actually block airflow at highway speeds. I had this issue back in the day when installing a v8 in my S10 pickup. Also experienced it with my 66 GTO, which had a cheap aluminum box shroud with two fans installed. Was fine around town, but would get too hot on highway. Removed electric fans, put a shroud around a mechanical clutch fan, problem solved.

Lastly, if you are not getting above 200 degrees, you should be fine.

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Old 02-15-2020, 12:25 PM
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The first thing you need to do is get an infared thermometer and verify that your temp gauge is accurate. Verify it through the range: my SW is accurate through some temps, then reads 20 degrees high in warmer temps.

Since you asked what we think; I run a 195 thermostat, so I certainly don’t think that seeing 200 on the gauge is something worth throwing money and Saturdays at - especially at 110 degrees outside temp.

I do agree with the earlier suggestion that you add a fan shroud. That likely will allow you to remove the pusher fans.

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Old 02-15-2020, 07:46 PM
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I need the electric fans for the AC and the fan is off my Firebird and is way too big for a shroud as it cuts into the underhood insulation now, do you think the water is travelling too fast to cool? i'm going to try a 180 deg. thermostat. The thing is, that was a really hot day, its not always that hot. I hear what your saying about the shroud etc. but I want to try the cheaper way out first.

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Old 02-15-2020, 07:49 PM
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Yes, you should have something to restrict flow. They sell aluminum washers with various size restricted holes we used to use in the circle track cars. Thermostat is best for street car.

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  #7  
Old 02-15-2020, 08:30 PM
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Quote:
Originally Posted by franky 455 View Post
I need the electric fans for the AC and the fan is off my Firebird and is way too big for a shroud as it cuts into the underhood insulation now, do you think the water is travelling too fast to cool? i'm going to try a 180 deg. thermostat. The thing is, that was a really hot day, its not always that hot. I hear what your saying about the shroud etc. but I want to try the cheaper way out first.
Water traveling too fast to cool, or pickup heat is a complete myth. What actually happens when a restrictor is added is coolant is pressurized by the water pump to minimize steam pockets. Heat transfers at the speed of electricity, or electrons, no water pump is capable of moving coolant faster than that. By eliminating steam pockets the block and heads are going to be covered by liquid which transfers heat much better than steam and air does. Many times people that have added a restrictor and cured their cooling problem misinterpret why the added restrictor worked, hence the myth that coolant passed too fast through the radiator to reject heat myths continue.

Boiler scale, or electrolysis in any part of the cooling system can, and will impede heat transfer so scale inside of the block will tend to insulate the cast iron and slow transfer of heat to the coolant. The other thing is to have plenty of air going across the radiator, engine driven fans usually are more efficient at cooling the radiator.

Some type of restrictor be it a thermostat or a washer should be in the system to minimize steam pockets that will impede cooling. Pontiac engineers made pulleys to speed up the waterpump (more RPM) on HD and cars with A/C, so obviously they had no misgivings about coolant traveling too fast through the system to take on, or radiate heat during engine operation.

The HD cooling systems also held more coolant by having 4 core radiators, which also increased the cooling area of the radiator. Increasing the capacity of coolant in the system will also get a marginal system to work more efficiently.

After fighting to keep oval track Pontiacs cool, these are the things I have found that can cause, and cure overheating.

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  #8  
Old 02-16-2020, 08:18 AM
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Thanks everyone for the comments, I have installed a 160 deg. thermostat and see how it goes on the next scorcher.
Cheers.

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Old 02-17-2020, 01:21 AM
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A 160 degree t-stat isn't going to make any difference. Once it opens up, be it at 160 or 180 degrees, it's all the same.

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  #10  
Old 02-17-2020, 05:06 AM
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I might be wrong, but I would rather have the water flowing through at 160 rather than letting it get to 180 then start circulating, make sense ?

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Old 02-17-2020, 06:35 AM
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I had a 160 high flow in my old 455 and at speed never went over 160, but in heavy traffic or stopped for a time would creep up to 200 , get moving and back to 160 , I live north coast nsw and would put a 180 in winter to keep the temp up. John L.

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Old 02-19-2020, 06:14 PM
70GS455 70GS455 is offline
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If its traveling too fast thru the radiator, it's also traveling too fast thru the engine

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  #13  
Old 02-19-2020, 08:34 PM
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There is no such thing as traveling too fast. Flow rate is part of the heat transfer equation, the higher flow rate, the less BTU per unit mass is transferred but you are moving more units of mass. High flow rates can also aid in creating turbulent flow, which typically helps keep heat insulating laminar flow to a minimum.

The problem with using a 160 thermostat in an engine with borderline cooling is that it reduces the thermal efficiency of the radiator. A radiator needs a Delta T, (difference in temp) between the water and the air to efficiently transfer heat, the lower the delta T between the water and the air, the less efficiently the radiator will remove heat from the water. On a 100 degree day, with a 160 stat, you have a 60 degree Delta T, with a 180 degree stat you have a 80 degree Delta T ... which means the radiator will remove more heat per unit mass from the water. The cooling systems are designed around a range of delta T conditions, flow rate of the pump, size of the radiator, fan design, shroud design ... all assume a minimum delta T based on the OEM thermostat specs.

If the cooling system and thermostat are operating as the should a 180 degree thermostat should keep the engine at 180 (+/- 5%) in ALL conditions. If it doesn't then the cooling system is not up to the job.


Last edited by dataway; 02-19-2020 at 08:39 PM.
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Old 02-19-2020, 10:51 PM
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^^^^^
What he said.

George

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  #15  
Old 02-20-2020, 12:52 AM
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Default Cooling System Balance

The cooling system if sized correctly, will be able to remove approximately 110% of the maximum heat generated by the engine. The basic components and function are:
1. The radiator: it transfers heat from the engine cooling system to the ambient air
2. The engine coolant system: it transfers heat from the engine to the radiator

The engine creating heat and the cooling system removing heat need to be in balance for the engine temperature to remain constant. This is the primary purpose of the thermostat.

In the case of a 180° F. version, the coolant flow rate of a cold engine is very low until it approaches approximately 160° F. Beyond that, the thermostat begins to open and by 180° F. it should be open enough that the coolant flow rate is approximately 60% of maximum along with the engine temperature being constant. Assuming this is the case, the thermostat opens or closes slightly based on the heat load.

This is an oversimplification of course but the thing to remember is that if the thermostat is not in the cooling system then there is not a way to control the amount of heat being removed or the temperature of the engine.

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Old 02-23-2020, 09:28 AM
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Quote:
Originally Posted by franky 455 View Post
I need the electric fans for the AC and the fan is off my Firebird and is way too big for a shroud as it cuts into the underhood insulation now, do you think the water is travelling too fast to cool? i'm going to try a 180 deg. thermostat. The thing is, that was a really hot day, its not always that hot. I hear what your saying about the shroud etc. but I want to try the cheaper way out first.

Get rid of that dam hood insulation. Shut the A/C till you get your problem under control. Use a thermostat that works properly. Like Napa sells 160deg. Do not use Mr Gasket thermostat as there junk.
I would also get rid of the puller and pusher fans. Get a proper shroud on that thing.

Use a Radiator like griffin sells 2 one inch cores.
Verify your temp with a new gauge.
Check air fuel ratio and also check timing on the engine like initial, mechanical and vacuum advance if your running a can.


Charles

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Old 02-24-2020, 01:51 PM
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The proper shroud and the the core support baffles are a HUGE deal on an AC car. You have to have them or you'll have problems. The mechanical fan will move way more air than the electric fans if the shroud is correct and the fan correct.

You could probably save all kinds of weight and complexity under the hood if you used the right OEM fan, shroud, lower radiator seal, frame horn seals and thermostat.

The way your mechanical fan is setup now it's just using up HP circulating air hot air around under the hood. I doubt it's pulling any air at all through the radiator at all.

To be honest, with that setup you have now, the first thing I might try is removing the mechanical fan altogether. If the electric fans are doing their job you shouldn't need the mechanical fan, you've got a decent amount of potential cooling power there. I'd bet the prop wash from the mechanical fan is destroying the efficiency of the electric fans.

That has to be one of the worst mechanical fan-to-radiator arrangements I've ever seen But ... beautiful car.

  #18  
Old 02-25-2020, 11:25 AM
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ZeGermanHam ZeGermanHam is offline
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Agreed, that fan setup is working against you. I'd pull the electric fans and install a proper factory fan shroud, radiator seals, and ensure your clutch fan is the correct diameter and offset relative to the shroud. My brother's Butler 461 was plagued with overheating for years. After going back to a factory fan and shroud setup, the cooling issues went away.

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Last edited by ZeGermanHam; 02-25-2020 at 11:42 AM.
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