The stocker maybe more elliptical, but I would think that the first pass or so of the sanding putty would stip out most of the casting flash. Then that would make it less elliptical. But continuing passes will hit the outside of the turns in the pipe and that caused them to preferentially sanded.
When I was doing my manifolds, the outside of the turns was very smooth, but the inside of the turn was still slightly bumpy. By turn, I am talking about the final turn at the exit of any of the runners on the upper IM. Anyway, 6 hours with a die-grinder and hand sanding took care of any irregularities.
warmonger
