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Old 01-02-2020, 05:35 PM   #1
chiro
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Default Flathead V8 operating temp?

Hi all,
1930-'31 Ford coupe AV8 hot rod. '39 trans, banjo rear, closed driveline. 59AB bored .030, stock cam, two carb manifold with Holley 94's, Edelbrock heads. 150 psi compression in all cylinders. Runs great.

My 59 AB runs very cool. When I first completed my build it was running only at 140 degrees and not running well, stumbling a lot, so I put the Volvo thermostats in it at 170 degrees. All was good. Engine ran much better settling in it about 160 degrees during the warmer months. However in colder weather like now the engine settles in at 150-160 degrees and does not run as well, stumbling a bit but not as terribly as when it was running at 140 degrees initially. The cooling system is obviously in very good condition, able to keep the flatty well below overheating even in very high outside temperatures.

My question is, what exactly is the correct operating temperature for my flatty and should I go to a higher temperature thermostat as the engine seems to run better when it is at a higher operating temp. I'm thinking it should be running about 180 degrees. any suggestions?
Thanks,
Andy
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Old 01-02-2020, 05:58 PM   #2
51 MERC-CT
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Default Re: Flathead V8 operating temp?

Go with the 180's
To address the stumbling try moving the accelerator pumps to the outward (winter position)
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Old 01-02-2020, 06:20 PM   #3
JSeery
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Default Re: Flathead V8 operating temp?

The hotter the better within the limits of other factors around the engine. With a pressurized system more modern engines are capable of running at higher temperatures. Gasoline engines are heat engines and any heat lost to the cooling system is lost energy. There are practical limits on a flathead in an enclosed engine compartment. 195 deg would be a good operating temperature to me, but 190 might work better in some applications. I would consider 180 to 185 as a minimum. In the early years there were limits imposed but non-pressurized systems and antifreeze types. In the later Flathead years Ford used a pressurized system and with better antifreeze increased the recommend operating temperatures stating better lubrication and increased efficiency.
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Old 01-02-2020, 06:39 PM   #4
G.M.
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Default Re: Flathead V8 operating temp?

Quote:
Originally Posted by chiro View Post
Hi all,
1930-'31 Ford coupe AV8 hot rod. '39 trans, banjo rear, closed driveline. 59AB bored .030, stock cam, two carb manifold with Holley 94's, Edelbrock heads. 150 psi compression in all cylinders. Runs great.

My 59 AB runs very cool. When I first completed my build it was running only at 140 degrees and not running well, stumbling a lot, so I put the Volvo thermostats in it at 170 degrees. All was good. Engine ran much better settling in it about 160 degrees during the warmer months. However in colder weather like now the engine settles in at 150-160 degrees and does not run as well, stumbling a bit but not as terribly as when it was running at 140 degrees initially. The cooling system is obviously in very good condition, able to keep the flatty well below overheating even in very high outside temperatures.

My question is, what exactly is the correct operating temperature for my flatty and should I go to a higher temperature thermostat as the engine seems to run better when it is at a higher operating temp. I'm thinking it should be running about 180 degrees. any suggestions?
Thanks,
Andy
I would shoot for the 175 to 180 range. If you get hotter then that you are going to have problems on a 100 degree day. Make sure the stats you use have large flow opening or you won't get enough flow the system. G.M.
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Old 01-02-2020, 08:42 PM   #5
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Default Re: Flathead V8 operating temp?

Try a little choke when it is running cool and stumbling. If that cures the stumble you may need to go up a size on the main jets. Or, - just use the choke.
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Old 01-02-2020, 09:17 PM   #6
JayChicago
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Default Re: Flathead V8 operating temp?

The physics cited by JSeery seems to make sense to me. "The hotter the better within the limits of other factors around the engine."

I disagree with the notion that using a higher temp thermostat is going to cause problems on a very hot day. On a very hot day, every thermostat is going to be wide open, regardless of its initial opening set point.

I'm skeptical of the common idea that we need large-opening, "full flow" thermostats. I suspect the limitation on how much water can move through the system is how much the pumps can push through the narrow water jackets in the block. As long as the thermostat opening is large enough to handle what gets delivered to it, a larger opening there isn't going to have any benefit. I suspect the standard thermostats are large enough, or the Ford engineers would have designed them bigger.
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Old 01-03-2020, 07:31 AM   #7
mfirth
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Default Re: Flathead V8 operating temp?

I'm in norhtern Ohio & run 180 stats in my 52 Victoria with an 8BA. Even on the hottest days it runs 180-190 degrees & performs well.
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Old 01-03-2020, 08:38 AM   #8
Ol' Ron
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Default Re: Flathead V8 operating temp?

Yes, 180/200.
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Old 01-03-2020, 10:58 AM   #9
RalphG
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Default Re: Flathead V8 operating temp?

Stumbling and poor cold response might just indicate a plugged exhaust crossover under the carburetor?
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