Early A with 340 Exhaust question

I didn't know Muratic acid would eat cast iron. LOL

you messin' with me? Pickin' on the slow guy? lol...

I mean.. it's acid so.... should corrode the hell out of it. I'm interested in how it's controlled etc. Seems like a really good idea for "smoothing" things out, like that abrasive goo porting, "sort of"...