This topic came up in another post so I'm just starting a new post on this topic. The question was asked by
@dusterbing the peace if testing had been done comparing a CNC ported ribbed finish to a smoothed/sanded finish. Here's one initial test on a factory CNC'd Speedmaster intake port. As a first test, the CNC ribs are smoothed out with a 36 grit cartridge roll. This is a fairly rough finish. In fact, the CNC finish feels smoother that the 36 grit. This CNC finish has a toolpath step length of about 0.040", which is pretty tight. Because the CNC cutting tool is a ball of about 3/8" to 1/2" diameter, the wider the toolpath step length, the rougher the washboard effect. Wider tool paths would make the valley to mountain top dimension greater, which would create a rougher texture.
Here's the results. I want to go on and smooth it down some more, especially in certain areas. Interested in the comments first.
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