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Discussion Starter #1
New waterpump,radiator, hoses,and had to bad thermostat s,running without one now still over heated.326 was rebuilt about 200 miles ago,radiator was also..any thoughts?
 

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The Pontiac water pump to intake opening and the metal gaskets have to be set up correct,...that is a common problem on pontia so.....


but a bad fan clutch can cause it as well, blocked passages even a blocked exhaust or stuck heat riser in exhaust manifold can make it run hot.....



I would check the fan clutch and put in a thermostat......make sure you have no hidden anti freeze leaks
 

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Are you just running hot, overheating to the point of the pressure cap blowing, or does the cap blow after you shut off?
 

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Discussion Starter #4
It seems to run hot then boils over into the Reservoir two thermostats have been bad DOA I took the thermostat out this morning dropped it into some hot water it opened at 211 Degree. it was supposed to open at 195 I did exchange the bad thermostats and got a new one set to open at 180
 

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Discussion Starter #5
I have just a solid original type fan hooked onto the water pump so it turns constantly and also I have headers not a manifold which of course the headers get pretty warm
 

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I'd venture to say 95% of overheating issues on these cars are caused by improper timing. I'd start checking there with a timing light and vacuum gauge. Best to check total timing and not just static. If all is well, move onto some of the suggestions here including the water pump divider clearance and the fan clutch. Also, when installing the t-stat try drilling a couple 1/16" holes 180 degrees apart on the outer rim. This allows some air to move through the system and prevents air lock heating issues.

There's quite a few threads on the board covering this topic so you might find some good solutions by doing a forum search. Good luck and post back your findings. Once you narrow down probable causes we should be able to help pinpoint your issue.
 

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Is the new thermo installed? Did you test it? Sorry to be Irish and answer a question with a question. With a rebuilt motor it could be a lot of things, starting as Lemans Guy said with a bad install of the WP. My '67 GTO ran hot due to timing and mixture.
 

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Discussion Starter #8
No I have not installed the new thermostat yet I did however run it without the thermostat and it did not overheat
 

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Make sure you have the correct radiator cap on. I changed mine from 15psi to 16psi when I was having issues, and it solved the problem.

Also, check to see if your bottom radiator hose is pinching - may have to add a spring.

Couple easy things to check first...
 

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Keep in mind that with only 200 miles on your engine, it will run a bit hotter. When it's broken in at 500-1000 miles, it will cool down a bit.....like 10-20 degrees.
 

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This is true, my temps dropped from 225-230 to 200-210 after 350 miles.
Took another another run today up the mountain to Running Springs and got the skunk eye from the CHP, I may have been going a little over the speed limit.
:)
 

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Those CHP guys are just kids. They used to be The Man, but now, just young jocks. No such thing as a low profile '67 GTO in this day and age, even a silver one. The movie Triple X made sure of that!
 

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It sure gets a lot of attention that's for sure!
She got a wash and wax today for her ride out Route 66 tomorrow, I will post some pics if I find a good spot to take some.
 

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I think Lemans guy was on the right track with the possible answer. The water pump vane-to-divider plate clearance has to be right, or the pump won't be pushing coolant through the engine nearly as efficiently as it should. Instead coolant will just slosh around rather than circulate. There is a YouTube video that describes this:

https://www.youtube.com/watch?v=UdyAo5546JQ
 
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