[sjdiesel]

Finally got my car back on the road and have some questions about how the car is cooling. As summer is approaching, I have concerns I will not be able to keep the car cool on the hot days.

Car runs about 170ish around town and about 185ish on the highway when it is about 60-65 degrees out. Highway speeds are 60-65mph / 2400-2700 RPM’s. Just last week I was driving the car home from work and it was 90 degrees out and on the side streets, the car stayed about 185ish and jumped to 205-210 on the highway. Seems like engine speed is playing a big part in cooling. I also notice the temp creeps up on some of the larger hills.

Cooling system specs:

• Iron heads and iron intake
• Cold case radiator
• Dual Derale fans 16825
• 7.5” crank pulley
• 8” waterpump pulley
• Flowkooler 8 bolt hi volume cast water pump w/ billet aluminum impeller
• New timing cover from Butler
• 50/50 o’reillys coolant/distilled H2O
• 160 t-stat

So What do you guys think? Are these normal temps? Is the pump turning too fast on the highway?

[ZeGermanHam]

Although I don't think those numbers are anything to worry about in terms of being too hot, it is odd that your engine is heating up when driving on the freeway.

My '66 has a 400 with iron heads & intake, as well as a Cold Case radiator and an Edelbrock high flow water pump. It'll hold steady at 190F at 55mph (~3k rpm for me) even in 95F humid days. And if I'm hotter than that in the city, driving on the freeway cools it back down.

I'm sure others here will have more good insight, but maybe you are leaning out too much?

[Goatracer1]

My 67 ran hot on the hiway with 3.89 to 1 gears and an T400 trans. Went to an OD trans and the temp dropped at least 20 degrees. Sometimes more. Never had a heating problem again.

[MUSLCAH]

My 67 will run 205 on the Highway on a hot day.....get off the highway and goes down under 200....good enuf. Have the 7 blade fan with hays super clutch....radiator is the original Harrison with a desert cooler core...and fan shroud...stock water pump with the defector plate adjusted real close without hitting the impeller.

[chrisp]

Rpm's build heat / lean carb jetting will run hot

[gtofreek]

I've never been able to keep a 64-67 GTO cool with electric fans. Came to the conclusion that the fan motors block off too much radiator area that these small radiators can't afford to lose. In every case, when I went back to manual fan, no more overheating. This makes sense since the engine runs warmer on the freeway. Too much radiator being blocked off and can't get air through it.

[Ccass]

Originally Posted by sjdiesel

Finally got my car back on the road and have some questions about how the car is cooling. As summer is approaching, I have concerns I will not be able to keep the car cool on the hot days.

Car runs about 170ish around town and about 185ish on the highway when it is about 60-65 degrees out. Highway speeds are 60-65mph / 2400-2700 RPM’s. Just last week I was driving the car home from work and it was 90 degrees out and on the side streets, the car stayed about 185ish and jumped to 205-210 on the highway. Seems like engine speed is playing a big part in cooling. I also notice the temp creeps up on some of the larger hills.

Cooling system specs:

• Iron heads and iron intake
• Cold case radiator
• Dual Derale fans 16825
• 7.5” crank pulley
• 8” waterpump pulley
• Flowkooler 8 bolt hi volume cast water pump w/ billet aluminum impeller
• New timing cover from Butler
• 50/50 o’reillys coolant/distilled H2O
• 160 t-stat

So What do you guys think? Are these normal temps? Is the pump turning too fast on the highway?

210 is a bit higher than I'd like to see you run. That uphill and highway increase has me thinking you have a volume issue. Which Cold Case Radiator did you purchase? What part number?

[Ccass]

Originally Posted by MUSLCAH

My 67 will run 205 on the Highway on a hot day.....get off the highway and goes down under 200....good enuf. Have the 7 blade fan with hays super clutch....radiator is the original Harrison with a desert cooler core...and fan shroud...stock water pump with the defector plate adjusted real close without hitting the impeller.

How about doing a test with a Cold Case radiator and then report back to everyone here? I bet CC can get you down under 200 on the highway and under 185 idling without changing anything else.

[Squidward]

Originally Posted by gtofreek

I've never been able to keep a 64-67 GTO cool with electric fans. Came to the conclusion that the fan motors block off too much radiator area that these small radiators can't afford to lose. In every case, when I went back to manual fan, no more overheating. This makes sense since the engine runs warmer on the freeway. Too much radiator being blocked off and can't get air through it.

I'm with this. I tried an electric fan in my 67 Firebird, and it would idle with a/c on in 115 degree weather all day long. Get it up to cruise speed on the highway, and it would creep. I went mechanical fan and clutch to solve the problem. I also suspected the electric fans got to a point where they impeded highway speed airflow.

What size water pump pulley are you using? Smaller diameter pulleys spin the pump faster, equalling more coolant flow. I run 6.5" pulleys out here in AZ.

[Ccass]

Originally Posted by Squidward

I went mechanical fan and clutch to solve the problem. I also suspected the electric fans got to a point where they impeded highway speed airflow.

What size water pump pulley are you using? Smaller diameter pulleys spin the pump faster, equalling more coolant flow. I run 6.5" pulleys out here in AZ.

Agree!

and good questions!

[sjdiesel]

Originally Posted by Ccass

210 is a bit higher than I'd like to see you run. That uphill and highway increase has me thinking you have a volume issue. Which Cold Case Radiator did you purchase? What part number?

RPE38L

[sjdiesel]

Interesting thoughts on the mechanical vs electric fan setup. This actually crossed my mind but I thought no way sooo many people run electric fans with excellent results. I still have the factory 7blade fan with a good clutch and repo shroud I could try and see if that helps things

[MUSLCAH]

Originally Posted by Ccass

How about doing a test with a Cold Case radiator and then report back to everyone here? I bet CC can get you down under 200 on the highway and under 185 idling without changing anything else.

The car is matching #’s ...so I wanted to make the Orig Harrison Rad work....and am happy with the results.

[sjdiesel]

Originally Posted by Ccass

210 is a bit higher than I'd like to see you run. That uphill and highway increase has me thinking you have a volume issue. Which Cold Case Radiator did you purchase? What part number?

Correction I have the 36L. Not the 38L

[Ccass]

Originally Posted by sjdiesel

RPE38L

That model is dual 1". We have since introduced a SD/HO version of the 64-67 GTO radiators for 'super duty' needs. You may have a few other things going on that could help lower temps but if you upgraded to the SD version, your temps would remain steady. No higher than 190.

I know you probably felt the RPE38L would be your last radiator you'd need but many cars are on that bubble. Yours is one of them. Back then CC didn't have a higher capacity option.

If you want to consider this option, PM me and we'll figure something out. I think everyone would like to be able for you to come back on this topic and get an update on how the upgrade affected the temps.

[Ccass]

Originally Posted by sjdiesel

Correction I have the 36L. Not the 38L

Even more of a reason. That is the shorter unit. the 38L was the bigger ac version.

[sjdiesel]

Ok so I removed the electric fans and installed my factory 7 blade mechanical fan, clutch and shroud. My factory shroud was cut to fit an incorrect radiator a long time ago so it isn’t the nicest. I ordered a repo one from Ames that will be here next week. Anyways the car runs MUCH cooler on the freeway. Granted it was much cooler today (between 66-70) but it stayed at 180 on the freeway all the way home and never saw temp creep on the hills.
Now the issue is running about 195 or hotter on side streets. I have a feeling the new shroud will help that but I have my reservations.

One question on the mechanical fan and clutch setup: how far should the fan sit inside the shroud? Is a spacer needed between the pulley and clutch to make it closer?

[ZeGermanHam]

Originally Posted by sjdiesel

Ok so I removed the electric fans and installed my factory 7 blade mechanical fan, clutch and shroud. My factory shroud was cut to fit an incorrect radiator a long time ago so it isn’t the nicest. I ordered a repo one from Ames that will be here next week. Anyways the car runs MUCH cooler on the freeway. Granted it was much cooler today (between 66-70) but it stayed at 180 on the freeway all the way home and never saw temp creep on the hills.

Now the issue is running about 195 or hotter on side streets. I have a feeling the new shroud will help that but I have my reservations.



One question on the mechanical fan and clutch setup: how far should the fan sit inside the shroud? Is a spacer needed between the pulley and clutch to make it closer?

The fan should be positioned about halfway into the shroud. Also, how fresh is your fan clutch?

[sjdiesel]

My fan is not even inside the shroud. And there are gaps all around the shroud to radiator.

Clutch is probably 20 years old but has little use. It feels nice and tight when warm.

[ZeGermanHam]

Originally Posted by sjdiesel

My fan is not even inside the shroud. And there are gaps all around the shroud to radiator.

Clutch is probably 20 years old but has little use. It feels nice and tight when warm.

If your fan isn't even in the shroud, it's not doing you much good. It won't be able to make any suction to pull air through the core of your radiator, which means it's basically useless at that point. I think you found the reason for getting hot at lower speeds.