If you're referring to the baffle you can see when you look through the filler cap, removing that will make the radiator less efficient. If the radiator is clear, the hot water will run through the tubes in the middle of the core only and will not cool as well as if it were spread over the whole width (and all tubes).
I have a radiator with a honeycomb core which is nice and clear but honeycomb is not as efficient as a modern core. I'm thinking seriously about having it re-cored with a modern 3 row core. I expect that will be so efficient, I'll have to use a thermostat for ordinary running but I'
I'll have plenty of cooling up my sleeve for when I towing in the heat up north.