# Looking for help getting my 68 GTO to run cooler.



## mcmsmsc (Aug 8, 2020)

Have a 68 GTO with A/C and stock 4core Harrison radiator, stock fan no clutch, should it have one? 190 thermostat. Car is running 210 to 220, to hot for me, what set up works best to get it running cooler? Want to try and keep the stock look but willing to upgrade the water pump to get it running cooler. Thanks for the help in advance.

Mike


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## O52 (Jan 27, 2019)

The A/C equipped cars came with HD cooling which meant a 7 blade thermostatic (clutch) fan. 
There's a few things that can help but here are two primary items that need to be looked at. First replace the thermostat with a 180*. Secondly is to inspect the water pump. It should have a cast impeller and should be clearanced. By that I mean, on quite a few rebuilt pumps, the impeller was pushed down to far allowing to much clearance between the pump vanes and the sheetmetal divider pates. This allows the water to cavitate and recirculate within the pump itself with poor cooling as a result. 
There are other causes such as a missing fan shroud and the rubber frame horn shields. 

Take a look at this regarding water pump impeller clearance. Its a long read but very informative.






Chalk up one more for the cast impeller. - PY Online Forums - Bringing the Pontiac Hobby Together
 

Chalk up one more for the cast impeller. Heating & Cooling TECH



forums.maxperformanceinc.com





Another cooling thread.






21 Reasons why your engine may run Hot - PY Online Forums - Bringing the Pontiac Hobby Together


21 Reasons why your engine may run Hot Heating & Cooling TECH



forums.maxperformanceinc.com


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## Lemans guy (Oct 14, 2014)

Great advice, you need a thermostatic fan clutch and shroud as 052 said, you also need your rubber in front and over the wheel wells next to the engine. Some guys remove those and it interrupts the flow of cooling air.


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## Jimbullets (Aug 9, 2020)

mcmsmsc said:


> Have a 68 GTO with A/C and stock 4core Harrison radiator, stock fan no clutch, should it have one? 190 thermostat. Car is running 210 to 220, to hot for me, what set up works best to get it running cooler? Want to try and keep the stock look but willing to upgrade the water pump to get it running cooler. Thanks for the help in advance.
> 
> Mike


Go to 160 thermostat and flex fan , I have a had several 68's and I run them hard ,fan shroud is a must ,160 thermostat,flex fan and four core Radiator , Jimbullets


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## Jimbullets (Aug 9, 2020)

I hope this helps You ! I own Four GTO'S now


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## BearGFR (Aug 25, 2008)

If you're running an engine driven fan, you definitely need a clutch. The purpose of that clutch is to limit the maximum rpm the fan is allowed to turn, because spinning it faster doesn't move more air. In face, it starts to act more like a solid disk than a fan.

Bear


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## mcmsmsc (Aug 8, 2020)

O52 said:


> The A/C equipped cars came with HD cooling which meant a 7 blade thermostatic (clutch) fan.
> There's a few things that can help but here are two primary items that need to be looked at. First replace the thermostat with a 180*. Secondly is to inspect the water pump. It should have a cast impeller and should be clearanced. By that I mean, on quite a few rebuilt pumps, the impeller was pushed down to far allowing to much clearance between the pump vanes and the sheetmetal divider pates. This allows the water to cavitate and recirculate within the pump itself with poor cooling as a result.
> There are other causes such as a missing fan shroud and the rubber frame horn shields.
> 
> ...


I will check out the article, thank you. I know I have replaced the pump probably 20 years ago now but there was no clutch on it then and it is the 5 blade 18" fan. I will look for a 7 blade fan and a thermostatic clutch fan. Thanks.


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## mcmsmsc (Aug 8, 2020)

Jimbullets said:


> Go to 160 thermostat and flex fan , I have a had several 68's and I run them hard ,fan shroud is a must ,160 thermostat,flex fan and four core Radiator , Jimbullets


The fan shroud is still there and I will get a cooler thermostat. It also sounds like I need to get a clutch fan and try and locate a 7 blade fan. Thank you.


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## mcmsmsc (Aug 8, 2020)

Anyone got pictures of the front of the motor for the 68 with the clutch fan. I assume I still need the spacer for the clutch.


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## Lemans guy (Oct 14, 2014)

Just know there are 2 versions of clutch fans,...one is rpm’s activated...one is thermal...

make sure you get the thermal one as often the other one is purchased cause it is cheaper..

but does not cool good, thermal has a spring on the front


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## BLK69JUDGE (Jun 10, 2010)

my ole 68 YZ HO 400

no spacer .... requires studs lock washers and nuts


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## O52 (Jan 27, 2019)

Lots of factory fans on Ebay, You want the 19 or 19 1/2" fans part numbers 9784546, 9796134, or 9796372. 

This is a heavy duty fan clutch. will work well for your application. 









1968 PONTIAC GTO Hayden Automotive 2947 Hayden Fan Clutches | Summit Racing


Free Shipping - Hayden Fan Clutches with qualifying orders of $99. Shop Fan Clutches at Summit Racing.




 www.summitracing.com





This is the standard replacement. Replaces what came with the car originally. 









1968 PONTIAC GTO Hayden Automotive 2705 Hayden Fan Clutches | Summit Racing


Free Shipping - Hayden Fan Clutches with qualifying orders of $99. Shop Fan Clutches at Summit Racing.




www.summitracing.com





If the radiator hasn't been look at for 20 years it may be time to take it in and have it cleaned or recored.


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## O52 (Jan 27, 2019)

Heres is a good photo of the clutch fan from another view.


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## Jimbullets (Aug 9, 2020)

mcmsmsc said:


> The fan shroud is still there and I will get a cooler thermostat. It also sounds like I need to get a clutch fan and try and locate a 7 blade fan. Thank you.


A 7 blade stainless flex fan is what I use on all my GTO's and 160 thermostat fan clutch goes out too often and sitting in traffic flex fan works !


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## mcmsmsc (Aug 8, 2020)

Jimbullets said:


> A 7 blade stainless flex fan is what I use on all my GTO's and 160 thermostat fan clutch goes out too often and sitting in traffic flex fan works !


Where can I find a 7 blade fan?


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## Old Man Taylor (May 9, 2011)

I use a factory 5 blade flex fan with no clutch. I've had it on since the late 70's. When I raced the car I shifted at 6400 RPM. I bought it at a junk yard many years ago. I don't remember ever recording the part number, but I think it's a Chevrolet part. My engine seldom runs over 170 degrees. I put one on my station wagon, but the engine was quiet enough that I could hear the fan roar. My GTO is noisy enough that I don't hear a thing.


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## Jared (Apr 19, 2013)

If you end up pulling the water pump make sure to check and replace the metal sleeves and O-rings if needed. Depending on how long your engine has been together, the O-rings could be in poor shape.


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## O52 (Jan 27, 2019)

He has a 68 with the 8 bolt water pump. Different design internally.


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## mcmsmsc (Aug 8, 2020)

Are the Cardone water pumps any good? Looking at summit and the photo shows a cast impeller. Or should I be looking and something else.


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## O52 (Jan 27, 2019)

Cardone is one of the better rebuilders. A few years ago they were made aware by members of the Pontiac community of the problems with stamped impellers and excessive clearances of the impeller to divider plate(s). 

Now with that being said, I can't say for certain whether Cardone followed their advice or not. You'll find out when you open the box.

If you still have a factory water pump with a cast impeller send it to the Flying Dutchman in Oregon. It will come back better than new and with proper clearance






Home


Quality, warranted, rebuilt water pumps for over 20 years. 3 year unlimited mileage warranty! We rebuild and remanufacture water pumps for most import and domestic automobiles, including antiques and classic cars.



water-pump-rebuilders.com


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## mcmsmsc (Aug 8, 2020)

O52 said:


> Cardone is one of the better rebuilders. A few years ago they were made aware by members of the Pontiac community of the problems with stamped impellers and excessive clearances of the impeller to divider plate(s).
> 
> Now with that being said, I can't say for certain whether Cardone followed their advice or not. You'll find out when you open the box.
> 
> ...


I wish I would have kept the original one when replaced it 20 years ago.


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## Robert1965 (Jan 4, 2020)

I believe Butler sells a high performance water pump for a fair price. Maybe look at that. For an added bonus, Clearance issues should be eliminated with higher quality part.


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## MidnightAuto (May 28, 2018)

This is the 8 bolt, but here is my cooling story.









another water pump mod?


Hey guys - I am doing some work on cooling. Replacing the water pump and radiator. I am aware of the mod to tighten up the space between the back divider plate and the impeller, but I read about another mod that I wanted to get your opinion on too. My understanding is that the middle divider...




www.gtoforum.com


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## OLDSCHOOL71 (Jul 14, 2020)

mcmsmsc said:


> Have a 68 GTO with A/C and stock 4core Harrison radiator, stock fan no clutch, should it have one? 190 thermostat. Car is running 210 to 220, to hot for me, what set up works best to get it running cooler? Want to try and keep the stock look but willing to upgrade the water pump to get it running cooler. Thanks for the help in advance.
> 
> Mike


My 71 has a CSB in it, but it’s got a 3 core stock radiator with a clutch fan and I’ve driven it on 98 degree days in city traffic and it only pushed 195 degrees. I think a quality clutch fan will at least help with it. It might not be the 100% answer, but it should help.


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## driftercb (May 15, 2020)

mcmsmsc said:


> Have a 68 GTO with A/C and stock 4core Harrison radiator, stock fan no clutch, should it have one? 190 thermostat. Car is running 210 to 220, to hot for me, what set up works best to get it running cooler? Want to try and keep the stock look but willing to upgrade the water pump to get it running cooler. Thanks for the help in advance.
> 
> Mike


Have tried a shroud? Also I think the aluminum radiators run cooler. I have a flex fan which eliminates the fan clutch. I also used to take out me thermostat in the summer. A plate with a 5/" hole works well as a replacement for the thermostat. Hope these help, good luck.


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## driftercb (May 15, 2020)

MidnightAuto said:


> This is the 8 bolt, but here is my cooling story.
> 
> 
> 
> ...


To go to the 11 bolt water pump, I think you need to get an 68 & up timing cover and change all your pulleys to match the thicker cover. They make a high volume 11 bolt pump too.


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## O52 (Jan 27, 2019)

69 and up cover.


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