If get a cheap stethoscope to zero in the location of the noise, they are quite good at that. Most pinging noises posted here turn out to be exhaust leaks.
It doesn't matter as long as there is a mating surface between the header flange and cylinder head all the way around the port of sufficient width to seal it.ofcourse. But should I match the header port that is oval, or the port from engine that is rectangle. I’m guessing a rectangle to catch the corners?