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What is normal running temp for 225 slant six?
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Author:  georgesee [ Fri Apr 17, 2026 1:57 pm ]
Post subject:  What is normal running temp for 225 slant six?

I'd be interested in knowing what the normal and stable running temperature is for a slant six. I have a 65 dodge A-100 running at 195 which seems to be on the high side. And that is after some 10 minutes of driving on city streets. Is this considered too high? I'm wondering if my thermostat may be frozen and that is why? What is the best way to check if I have a bad thermostat? I am running an 180 thermostat.

Author:  Dart270 [ Sat Apr 18, 2026 4:29 am ]
Post subject:  Re: What is normal running temp for 225 slant six?

How are you measuring the temp? Do you have an aftermarket temp gauge with numbers on it? The stock gauges can be very inaccurate. 195 is not too high if it does not keep climbing and just stabilizes there.

Lou

Author:  georgesee [ Sat Apr 18, 2026 9:43 am ]
Post subject:  Re: What is normal running temp for 225 slant six?

Yes, I have a bosch temp gauge with numbers and it appears to read between 195-200-205. I am wondering if a high flow water pump would help lower the temperature?

Author:  georgesee [ Sat Apr 18, 2026 9:46 am ]
Post subject:  Re: What is normal running temp for 225 slant six?

I also burped the radiator by parking the truck on a steep incline and removing the radiator cap. I didn't really see any bubbles while I did this but I did notice that the coolant was moving so would this mean that the thermostat is not stuck?

Author:  Dart270 [ Sat Apr 18, 2026 11:29 am ]
Post subject:  Re: What is normal running temp for 225 slant six?

The temp will run a little hotter than the thermostat rating. The main thing is that it does not continue climbing if you are sitting idling or driving on the highway. 200 is a bit hot for that thermostat, so maybe there is some clogging in the radiator or inside the block.

Lou

Author:  SlantSixDan [ Sat Apr 18, 2026 1:49 pm ]
Post subject:  Re: What is normal running temp for 225 slant six?

Quote:
I'd be interested in knowing what the normal and stable running temperature is for a slant six. I have a 65 dodge A-100 running at 195 which seems to be on the high side.
The thermostat sets the engine's minimum operating temperature, not its maximum.

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