Lack of soffit vents with the use of ridge vents on a 1941 home
Adding a vent to the ceiling of your porch would only be beneficial if you open up any exterior windows and doors leading into the porch. Then you'd have air flow from outside through the porch and up into the attic. The only time it would be useful would be in the summer when you'd be replacing 130 degree air with 85 degree air. so yes, it would benefit in the summer. If you opened the doors leading to the porch from your living space in the summer, you'd be sucking AC air from the living space to the porch into the attic.... not too efficient.