I assume that you are using 1/4" inside diameter fuel line, not vacuum hose.
The inside diameter of 5/16" steel tube is about 1/4". However, there is less resistance to fuel flow inside the steel tube.
It probably will not be a limitation in most driving situations. If the hose is extremely long and you are running at a large throttle opening for awhile you might run out of fuel in the carburetor.
There are some really easy-to-bend steel tubes available at any auto parts store today. I suggest you consider that approach and avoid the fuel starvation concern plus eliminate a rubber fuel line hear a hot exhaust manifold.
