I know, another overheating issue. - Page 2 - Pontiac GTO Forum
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post #11 of 19 (permalink) Old 08-22-2019, 08:29 AM
 
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And make sure your fan clutch is the “Thermostatic” type....not the centrifigal type.....one runs with great cooling, the other does not.

They look similar just activate on temp.....which you want ....and not on RPM
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post #12 of 19 (permalink) Old 08-22-2019, 09:32 AM
 
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Dual 16in electric fans with shroud that pull at least 4,000-4,500 cfm. You get all the cooling at idle.

Also its not the worst to run in those temp ranges as long as your boiling the coolant and actually over heating. Higher pressure cap will raise the boiling point of the coolant even more.

Just as a comparison a lot of newer cars dont turn fans on high until 220.

2006 GTO M6

Motor - Stock with Vararam
Bunch of suspension
Bunch of brakes
Stock tune

365/368 std
12.81 @ 110.6 2.03 60'
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post #13 of 19 (permalink) Old 08-23-2019, 07:57 PM Thread Starter
 
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Thanks you guys for all the thoughts. I think I’ll try the bigger fan first! The radiator is only dropping the temp about 10-15 degrees I think it should be more like 30-40. So something’s a miss.
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post #14 of 19 (permalink) Old 08-28-2019, 06:54 PM
 
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Agree with the 4 core, but sounds like a fan issue. I would get the a/c style fan. See if it works better if not put it back on eBay. Also I remember reading an article many many years ago about a guy who's had a bad casting and one of the passages was greatly restricted. He had overheating problems since driving it off the lot. It took a complete tear down and inspection to finally resolve. The engine appears to be the only thing you didn't swap out or change. Sounds super frustrating
Good luck.
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post #15 of 19 (permalink) Old 08-29-2019, 05:37 AM
 
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I solved my cooling problems in my 66 389 tri-power with Evans waterless coolant. I don’t even run a shroud. The highest temp I’ve recorded was 205, that was in the 90’s sitting in my driveway idling. It’s expensive compared to antifreeze but well worth it
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post #16 of 19 (permalink) Old 08-29-2019, 05:39 AM
 
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I think you've got a lot of good input already but I wanted to add my $0.02. My '68 had similar issues at idle. In my case the problem was air flow. With the hood up it ran cooler or if I revved it to around 2000 rpm and held it the temp would drop. I eventually went to dual electric fans and all is well...even in the Texas heat.

You didn't say if opening the hood or raising the idle speed had any effect. In my experience if the fan is the issue those things would.

The fan's cheaper but I'm thinking four core radiator and I like aluminum.
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post #17 of 19 (permalink) Old 09-04-2019, 02:41 PM Thread Starter
 
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Quote:
Originally Posted by mikelly2 View Post
I think you've got a lot of good input already but I wanted to add my $0.02. My '68 had similar issues at idle. In my case the problem was air flow. With the hood up it ran cooler or if I revved it to around 2000 rpm and held it the temp would drop. I eventually went to dual electric fans and all is well...even in the Texas heat.

You didn't say if opening the hood or raising the idle speed had any effect. In my experience if the fan is the issue those things would.

The fan's cheaper but I'm thinking four core radiator and I like aluminum.
I’ve tried bumping up the idle while sitting, it didn’t really make a difference. I’ve also tried opening the hood with little change. The only thing that seemed to help was kicking the heater on. The car runs 190 all day regardless of the heat while moving, but as soon as it sits it gets hot. Maybe this engine combo just needs more radiator? I’d like to know if others running a 461 have had issues with the smaller radiator?
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post #18 of 19 (permalink) Old 09-04-2019, 02:44 PM Thread Starter
 
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Quote:
Originally Posted by XceedVne View Post
Agree with the 4 core, but sounds like a fan issue. I would get the a/c style fan. See if it works better if not put it back on eBay. Also I remember reading an article many many years ago about a guy who's had a bad casting and one of the passages was greatly restricted. He had overheating problems since driving it off the lot. It took a complete tear down and inspection to finally resolve. The engine appears to be the only thing you didn't swap out or change. Sounds super frustrating
Good luck.
XceedVne (A/C reference?) the engine was recently rebuilt and all passages checked. I removed the original engine and started with a near matching alternate block and heads. But the heating issue migrated to this engine also. During the rebuild I had the radiator gone through and I was told it was still in great shape by a reputable shop. It is the smaller 15” radiator though. It’s shrouded and sealed, has the 18” 7 blade fan, and new clutch. It sits nearly half in and half out of the shroud. But shooting it while operating it’s only dropping the temp 10-15 from top to bottom. I’ve thought about sticking in the Cold Case set up with electric fans but it pains me to change anything on the car that shouldn’t be there.
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post #19 of 19 (permalink) Old 09-05-2019, 05:46 AM
 
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If it runs 190 while moving I'd still be thinking air flow but if turning on the heater lowers the temp that kinda sounds like you need more radiator.

I hear Ya about changing to something that doesn't look stock but I like to drive mine and don't want to worry about it overheating. I live in East Texas where it gets plenty hot and the dual electric fans and aluminum radiator work for me.
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