@GTBOB
What is the inside diameter of the stock primary header tube?
The more time you have the better. This certainly isn't a project you can just fast forward on. It's very easy to be going on a bolt that takes 5 minutes to do, then the next bolt takes over an hour and you feel beat to death after it. Your plan sounds really solid and relaxing. Over the 4 days I got to enjoy time with my dad, shoot the shit and gameplan the next boltI'm gonna be doing headers myself soon. I plan to just take my time and spend like 2 hours a day on it until it is done.
I ground mine smooth on my 2013s stock headers. Not sure if it made any measurable difference.I measuring about 1.80" or 46mm at the flange but about .25" or 7mm down into the primary it tapers down because of the bead of weld inside to 1.50" or 38mm. Further in past the weld, it goes back to 46mm. If you could grind the weld down inside without compromising it, I would imagine there is some upper rpm power to be made.;)