[Jim Fodell]

My 67 gto overheats when i have to stop after driving for a while. Some bobcat item still remain, could the blocked heat risers be the cause? Also, the thermostat is at 180, would going to a 160 help? I would like to keep it original, but if the only way to cool is electric, I may have to go that way. Any thoughts?

[bendutro]

Thermostat is just a minimum, if you're exceeding 180°F now, a 160 will accomplish exactly jack and squat, and it's just too cold besides.
Shroud or no?
Is your water pump plate/impeller clearanced?
Fan blade count? spacer or clutch?

[george kujanski]

follow the link below; it's in the heating/cooling forum in the sticky at the top; "Chalk one up for the cast impeller"... alot of info there.

i assume you have checked for stuck thermostat, etc.

http://forums.maxperformanceinc.com/...d.php?t=411256

George

[Gator67]

Before you start replacing parts, consider the simple things. I know this might sound stupid, but first verify you're really overheating...don't just rely on the gauge or dummy light. Also check your tune...too lean or not enough timing will cause overheating problems. Check to make sure your vacuum advance isn't disconnected and is operating properly. You should not have to go with an electric fan to keep your car cool. I don't have electric fans on my cars and I drive them in the summer when it's 115 with no problems.

[fyrffytr1]

What, exactly is happening? Does the car get hard to start? Does coolant release from the radiator cap or does something else happen?

[boltbuster]

Check your upper radiator hose. Sometimes, if the hose is too short at the thermostat housing, the coolant ifs having to flow uphill, and therefore slower. I think that there may be a thread somewhere regarding that issue. Good luck!

[fyrffytr1]

One more question, did this just start or has been a problem since you got the car on the road?

[geeteeohguy]

If it only gets hot when you stop it, that's called heat soak, and is normal in very hot weather. Puking coolant is not. Is it puking coolant? Or is it just getting up to 230-240 when you shut it down? I run stock cooling systems on both my '65 and '67 and they don't overheat in 110 degree summer heat.

[GT182]

Jim I have the same problem with my 66. I have the correct 8 bolt water pump with the correct cast impeller, and a recored stock 3 row radiator, recore with more tubes and fins. So you are not alone.

I hate aluminum radiators but I'm seriously thinking of a Cold Case radiator. It looks just lie the Harrison but made out of aluminum. It seems guys are having better luck with aluminum so I'm thinking of giving it a try too.

Cold-Case Radiators is a division of Max Performance Inc.... formerly a division of Performance Years.
http://coldcaseradiators.com/

[fyrffytr1]

Originally Posted by GT182

Jim I have the same problem with my 66. I have the correct 8 bolt water pump with the correct cast impeller, and a recored stock 3 row radiator, recore with more tubes and fins. So you are not alone.

I hate aluminum radiators but I'm seriously thinking of a Cold Case radiator. It looks just lie the Harrison but made out of aluminum. It seems guys are having better luck with aluminum so I'm thinking of giving it a try too.

Cold-Case Radiators is a division of Max Performance Inc.... formerly a division of Performance Years.
http://coldcaseradiators.com/

Gary, I will let you know how the cold case works out. I have one on order from our host. Hopefully it will be here in a couple weeks.

[gtospieg]

I see where their warranty says "60 day COOL guarantee" if this rad doesn't run cooler than your current rad you can send it back for a full refund. Has anyone tested this rad without making ANY other mods? What were your results?

[fyrffytr1]

Originally Posted by gtospieg

I see where their warranty says "60 day COOL guarantee" if this rad doesn't run cooler than your current rad you can send it back for a full refund. Has anyone tested this rad without making ANY other mods? What were your results?

Like I told Gary, I will let you know what I find when mine gets here. There will be no other modifications done.

[gtospieg]

Good to know...curious to see if it actually makes a difference w/no other changes. I always hear people say aluminum is better than copper/brass but I haven't ever seen a test where the only change made was the radiator...

[GT182]

Ross, I'll be waiting. I just got back to work and I'm trying to save for one....

if the Warden will stop bugging me for money. I told her if she wants money to go get a job. Then she hit me. The doctors say her arm should heal with no problems in a few weeks. But for now she's eating with her left hand, and it ain't pretty.

[MUSLCAH]

I just got my Radiator back from Classic Radiator...they installed a 4 core desert cooler core onto my original Harrison Tanks.... 20-25 % more efficient.....more tubes and more fins per square inch. Don't forget the spring inside the lower rad hose. I'll let you know how that rad works ....when the car hits the road in May

[GT182]

MUSLCAH, I did the same thing and had a SLK core installed with my original tanks. No luck as it still over heats. I know a lot of it is heat soak, but sitting at red light for 10 minutes or so it still overheats.

And if an aluminum radiator doesn't work, I louver the hood like on the 68 Shelby Mustangs. Or maybe sell the car and buy that 68 Charger I saw online.

[MUSLCAH]

Originally Posted by GT182

MUSLCAH, I did the same thing and had a SLK core installed with my original tanks. No luck as it still over heats. I know a lot of it is heat soak, but sitting at red light for 10 minutes or so it still overheats.

And if an aluminum radiator doesn't work, I louver the hood like on the 68 Shelby Mustangs. Or maybe sell the car and buy that 68 Charger I saw online.

How hot is hot ??

[charles bledsoe]

At what temperature and time at that temperature do you get to damaging effects of the engine? I'm guessing the car would boil over and steam would come out of the hood before any damage could occur? Is this correct? I haven't experienced that since I was a teenager. I do not have a gauge, just idiot light on the 66....just curious.
Thanks.

[GT182]

Originally Posted by MUSLCAH

How hot is hot ??

I've seen it go up to 240 just sitting at a light. To me that's not heat soak. My first 66 GTO back in 1970 never overheated even on the hottest day of the year..... moving or sitting still. 389, 4 speed, and 3 row radiator.

I know part of everyone's overheating problem is that crap called Ethanol in our gas and the Octane used. Higher octane gas does keep my over heating down a little if I use 100LL aviation gas, but I can't get it all the time.

[lust4speed]

I have my original HO radiator equipped with a 16 year old Desert Cooler core, original HO fan, shroud that I purchased in 1967, added Vintage Air unit, and the car barely goes over thermostat in traffic or sitting at a light with the AC on.

I have friends that have tried all the different aluminum radiators, and we have found that everything cools the same if they are in good shape. I do run the Hayden Severe Duty 2797 fan clutch, and did change over to the AC pulleys after installing the AC unit. Stock HO has roughly* a 7" on bottom and 8" on top for about 12% under-driven water pump and fan. The AC pulleys are opposite with the 8" on the crank and 7" on the water pump for about a 14% over-driven water pump and fan. If you figure the difference between under and over driven you are moving about a third more air and coolant at any given RPM with the pulley change.

My water pump plates are tightly clearanced to the impeller, and in my case I'm running the stamped steel water pump impeller - people can claim how much better the cast iron is, but in back to back testing we could never measure any difference in performance. I also have tweaked the spring on the fan clutch to come in sooner.

Think the water temp light comes on at 240? That was the temp that we would pull off and shut down an engine. Think 260° would be getting critical.

* Pulley diameters are a little larger, but too lazy to dig up their exact size.