Here's pics of the primary intake ports hone with 3 grits of flexhones. Left-to-right they are 320, 240 and 180 grit. Looks like 120 grit will win out but I don't have one to test. I think I can find them in stock at one of my supply houses but 120 grit in hones is rare and hard to find. Many flex hones stop at 180 grit as they are "hones" and not grinders.

The little dimples you see in the pic are concave rather than convex. The are tiny little pockets rather than protrusions. All testing was done with the grit-count I mentioned and 30 seconds at 2400 RPM in a drill. If I can find the 120 grit flex hone it oughtta be about pefect.

I want the primary runners to have a good smooth finish as we remain in the primary runners from idle to 4100 RPMs when the secondary switchover occurs. That means that 66% of our off-idle acceleration RPM's intake air enters the combustion chambers thru the primary runners rather than the larger secondaries. This means that we need these runners to be paid as much, if not more, attention than the secondary runners which are only used from 4,100RPMs-to-redline... literally only 1/3 as much time as is spent in the secondary side of things in any low-RPM-to-redline run. This should demonstrate in a BIG way how woefully inadequate just porting the final 3.5" before that section dumps into the cylinder head is in terms of comparison.

The next picture is the opposite side of the intake manifold primary inlet ports. I'll leave them un-touched so you'll have some idea of difference in smoothness and polish affect of the flex hones.

I'll provide all necessary info on the flex hones themselves as far as size, grit, where to buy etc soon as I settle on a grit, count and sizes required.

UPDATE*: I just checked with my supplier and 120 grit flex hones are available in the sizes we'll need. More info on these related to price, sizes as the workshop progresses.