What size plug recommended for this cooling head?

extremeodd

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The heat range shouldn't affect whether it's running rich or not, that is purely on the carburetor. To some extent, the heat range will affect your cylinder head temperatures but it shouldn't be enough to affect your tune.

Heat ranges are important as you want the plug to get hot enough to "self-clean" but not so hot to cause "preignition".

If your plug is too cold, it will foul and fail in a fairly short time. If your plug is too hot, it can cause preignition which will drastically decrease power and has the potential to damage the motor.
 


inspectorcritic

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So that makes me wonder. If you're running rich, would you run a hotter or colder plug? What actual conditions define the "temperature" of your plug?

Nevermind, I think this link answered my question. https://www.ngk.com/learning-center/article/207/what-is-a-spark-plugs-heat-range
I think if your running rich to change the carb ring needle setting.
But I think the cooler the plug the leaner the mix cuz it ain't gonna burn it and you might get an overflow of oil in your crankcase that might lead to other problems.
The TR66 has the same # 4 heat value but it's antanomy is different wasn't hot enough being inside the fire bowl.
Well I'm not a internal combustion engineer it's trial and error here.
 

extremeodd

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The heat range of the plug doesn't affect how rich or lean a motor is nor does it cause incomplete combustion if it's too cold. If your running too cold of a plug on an engine that is running rich you will simply foul the plug in a very short time period as it isn't getting hot enough to self-clean (which is what the heat range is defining, how hot does the plug tip get) which then would start to cause incomplete combustion due to no combustion happening. Run cold plugs in hot weather and hot plugs in cold weather to keep the temperature high enough so they can self-clean but low enough not to cause preignition/damage to the plug.
 

inspectorcritic

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Well, I think the ambient air temperature has little to do with it a fire gets so hot and is isolated from surroundings maybe the plug has a cold starting point would have some bearing on but once up to operating temperature cold or hot weather has little play.
 

gary55

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Well, I think the ambient air temperature has little to do with it a fire gets so hot and is isolated from surroundings maybe the plug has a cold starting point would have some bearing on but once up to operating temperature cold or hot weather has little play.
why do you think you see more cars over heat in the summer then the winter? Could it be because they run hotter when it's hotter outside?
 

inspectorcritic

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why do you think you see more cars over heat in the summer then the winter? Could it be because they run hotter when it's hotter outside?
More cars overheat in the winter do to freezing busting various radiator & engine block parts. It could be minus 70° yet the cold is still not preventing overheating.
 

Frogslayer

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Yeah i live in Minnesota and have overheated a truck once in the due to freezing. Coolant tested good to -20 but i guess that wasn't enough. Temp was -16 and i was driving straight North into a 40 mile an hour wind at 60. That was a total fluke though I've overheated at least a dozen times with various vehicles in the summer.
 

gary55

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Yeah i live in Minnesota and have overheated a truck once in the due to freezing. Coolant tested good to -20 but i guess that wasn't enough. Temp was -16 and i was driving straight North into a 40 mile an hour wind at 60. That was a total fluke though I've overheated at least a dozen times with various vehicles in the summer.
Land of 10,000 lakes, and they were all froze solid that night.
 
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