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I have a 10 over 455/400 combo with vintage air and using a OEM clutch fan, the radiator has been cleaned and rodded, the water pump is new and the engine has been rebuilt. When it is really hot outside here in Missouri [105deg F] the temp gauge will hit 240.

What temp thermostat would you recommend? Any other suggestions?
 

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A few questions;

What year?

Trans type?

Car running hot when moving or stopped in traffic?

Is a fan shroud installed?

What is timing both initial and total?

Many reasons car is running hot, your answers will get us started in diagnosing.....
 

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#1 cause of cooling problems in Pontiacs is having the clearance between the divider place behind the water pump and the pump impeller too wide. Use the search tool here and you should find several threads containing information on how to set it properly. Another cause can be the "wrong" type of pump impeller (commonly happens with remanufactured pumps).

The factory cast impeller looks like this:


Stamped steel impellers like the one in the top example tend not to work as well




Bear
 

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Cool running.

I never though that i would have overdid it on a cooling system but i did. Pontiac engines do run hot. I installed a 3 core copper Radiator and a FlowKooler water pump. VERY IMPORTANT. Make sure the divider plates are installed and clearance is checked. For some odd reason people will leave them out. If you do, no matter what else you do the engine will always run too hot and 240° is wayyy too hot and you will ruin your engine. I live in the San Joaquin Valley in Ca (basically a desert) and even on 105+ days I will still be running at 180 ° at 55 on the freeway. I do have an auxilary electric fan that will kick on @ 200° if i have to sit in traffic. It rarely comes on even on the hottest days.

I did also install a high performance t-stat from Summit. I have to install a 190° t-stat because i can't maintain operating temp, if the ambient temp is under 85°

If you're running that hot I'll bet that your diverter plates are missing or installed wrong. They make a huge difference.



 
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