I know, another overheating issue. - Pontiac GTO Forum
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post #1 of 19 (permalink) Old 08-21-2019, 03:33 PM Thread Starter
 
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I know, another overheating issue.

I was hoping with a new engine would come a cooler running one but to no avail. I recently installed a 400 that’s been Stroked to a 461. When driving in stop and go traffic the engine, especially at idle is getting hot, like in the 215-225 range (It’s in the 90’s here in Utah btw). Things that have been checked/modified- Radiator (non-a/c was recently rebuilt. Flow Kooler water pump w/new baffle worked down tight onto the impeller. New Kaufman timing cover. Radiator shroud installed and sealed all around it. Water Wetter added to 50/50 mix. New heavy duty fan clutch. Belts checked. System has been burped. Hoses are new and stay to form also have spring in the lower. Timing is ran off manifold at about 14 degrees base. Carb has been jetted and rodded to run rich. When I turn on the heater to full it is dropping about 5 degrees.
Any ideas would be appreciated. I don’t know what to do next?
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post #2 of 19 (permalink) Old 08-21-2019, 06:19 PM
 
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Wish I could help you, but you seem to have covered alot of the bases. I know it can be frustrating. You mentioned having the radiator rebuilt. Was it the original one?? From what I read, aluminum appears to cool better then the factory copper/brass. Hope you get it figured out, Nicholas.
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post #3 of 19 (permalink) Old 08-21-2019, 06:25 PM Thread Starter
 
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It is the original. It was rebuilt by a quality shop that said it was still in great shape. I thought about an aluminum but I’m trying to stick with what appears stock.
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post #4 of 19 (permalink) Old 08-21-2019, 08:55 PM
 
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Garage
Don't assume your gauge is reading correctly. Purchase a laser temp gun at any auto store and shoot the cooling system in a bunch of places and see if it matches the gauge.

Then go from there.
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post #5 of 19 (permalink) Old 08-21-2019, 10:35 PM
 
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no mention of thermostat temp .... 185 ???
x2 on a temp gun so handy in so many ways

and what fan ???

https://www.ebay.com/itm/1964-64-196...H/372646039100
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post #6 of 19 (permalink) Old 08-22-2019, 12:25 AM Thread Starter
 
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Jim, sorry left that out. This is with an aftermarket I put in to back up the original gauge. The original runs much lower (maybe modded by Pontiac to do so?) I’ve shot it with the gun and it’s accurate. I’m running the 160 t-stat per Butler’s recommendation. The radiator in vs out is only cooling it about 15 degrees. It has the original fan blade as far as I know. It seems to be in good shape.
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post #7 of 19 (permalink) Old 08-22-2019, 01:47 AM
 
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Originally Posted by Dukes67 View Post
Jim, sorry left that out. This is with an aftermarket I put in to back up the original gauge. The original runs much lower (maybe modded by Pontiac to do so?) I’ve shot it with the gun and it’s accurate. I’m running the 160 t-stat per Butler’s recommendation. The radiator in vs out is only cooling it about 15 degrees. It has the original fan blade as far as I know. It seems to be in good shape.
I remember on my 66 the fan blade can be put in backwards. There is an IN and OUT stamped on the fan center that's hard to see.
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post #8 of 19 (permalink) Old 08-22-2019, 01:52 AM
 
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Originally Posted by Dukes67 View Post
Jim, sorry left that out. This is with an aftermarket I put in to back up the original gauge. The original runs much lower (maybe modded by Pontiac to do so?) I’ve shot it with the gun and it’s accurate. I’m running the 160 t-stat per Butler’s recommendation. The radiator in vs out is only cooling it about 15 degrees. It has the original fan blade as far as I know. It seems to be in good shape.
I remember on my 66 the fan blade can be put in backwards. There is an IN and OUT stamped on the fan center that's hard to see. I don't think mine was a clutch fan though but I could sure feel the air blasting rearwards when I straightened that out.
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post #9 of 19 (permalink) Old 08-22-2019, 08:12 AM Thread Starter
 
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The fan is on correct and is pulling air. Maybe it’s just time for a different radiator? I also replaced the exhaust manifolds when I put the engine in with Rare Exhaust and this seemed like it reduced the amount of air outflow area in the engine bay. Could that be a culprit? I’ve heard these engines run hot but I also run into guys that don’t seem to have any issues. Short straw syndrome?
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post #10 of 19 (permalink) Old 08-22-2019, 08:26 AM
 
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Duke, sorry you are having that problem,...non AC radiator would be a 3 core radiator. The AC is a 4 core as far as I know.

I use a 4 core Radiator with extra wide downtubes. No difference in external appearance to original radiator, except it does not have the stamped “Harrison” on the top.

Go to US Radiator website put in Pontiac and search around. Also call them they are very helpful, and really know the mounts and sizes etc.

That extra cooling from 4 core and larger than stock down tubes adds a bunch of cooling. My 461 runs at 180 has a 160 thermostat.

A couple of little things I drill 3 1/8 holes around thermostat ring to aid the air movement inside, also make sure your fan is half in and half out of the shroud,

and you may want a seven blade Pontiac fan that came on AC cars....much better.

So I would consider upping that Radiator, looks original and that fan as well...that is what the factory did because the condenser dropped all that heat in the engine bay.....let us know how you do.

Oh you will see Jimmy Shine endorsing US Radiator, they are both California shops, he has built a few cars,....and wants performance and original looks....good luck
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO General Discussion

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