Although it is difficult to tell what is happening by your description, I think I have a solution, or at least a place to start looking for a real answer.
I think your problem may be vapor lock. This occurs in aircraft more often because of altitude changes. If the temp gauge reaches half (on the gauge) that would indicate a normal operating temperature for most vehicles. A quick look at the instrument cluster will show most needles in the straight up position. This is by design so that when you see one needle pointing one way or another, you know there is an abnormal situation with just a glance.
If you are operating at the normal temperature, this may mean that one of your fuel lines, or fuel rails is being heated abnormally in the engine compartment. Perhaps a fuel line bracket is missing or broken causing a line to lay on a hot engine component such as the exhaust manifold or an oil line or a header or the engine block. You might also try wrapping your fuel lines in a heat reflective tape. Another suggestion is to fashion a heat shield under the carburetor.
However, you may have a different fuel delivery problem, such as debris in the tank, restriction in the fuel line or fuel filter, or tank pickup.
Here is an interesting article about vapor lock and it's prevention.
One more article on prevention.
I would be interested to know if any of this works.