Quote:
Originally Posted by freebeard
Three angle valve grind is pretty straightforward. Porting and polishing is a black art, at least it was in the mid-1950s.. Rough finish in some areas prefered.
Today we have extrude honing.
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I actually have some experience with extrude honing, and it's got nothing on plain old hand porting. Extrude honing is a very expensive service and the process doesn't remove a lot of material. Forcing a media thru a port/runner is not going to re-shape the port/runner for better average flow as if you were hand porting it. The media removes more material in areas of high flow better than areas of low flow which is not effective when compared to hand porting. At best, extrude honing can save a bit of time for the hand porter. But he's still going to have to go back in and get everything that extrude honing missed, which will be quite a lot.