It blocks it up!
I used rad weld in a 2.8 injection Capri to “get me home” which it did.
several years later the radiator needed repair so I took it out and sent it for rebuild. I decided I would replace the hoses at the same time. The bottom hose did a loop. To allow for alignment. Inside I found all the rad weld. The internal diameter reduced to about 3/4 of an inch.