318 cam and intake suggestions

I'm interested in the cam grinding process. How can they take a small cam like a stock 318 and grind It to make it bigger?( higher lift) do they weld to the lobes and add material or something?? Sorry if this is a stupid question but i really dont know and i really want to know lol.
Now let me say this right off. I have no experience with reground cams in automotive engines. My experience is with airplane engines on airboats. Your right. You don't make it "bigger". You re-grind and adjust in the rest of the valve train, ie longer pushrods, higher ratio rockers. Make sense?