If Silly Putty grew up and got a real job, it would be extrude honing
In the hunt for better engine performance, porting is a common method. The process removes material in critical areas to allow more air and fuel to flow through an engine. More air and fuel means better combustion and more power. But how do you accurately port complex interior shapes? Extrude honing.
Business Insider created a video which explains the process, and it is rather satisfying to watch the abrasive putty do its work. The result is similar to how most porting is done, where an abrasive bit attached to some form of rotary tool wears down existing material. But in this instance a silicone putty is impregnated with abrasive material and pushed through the metal. Just like sandpaper, the grit (or how aggressive the mixture is) can be adjusted to fit the amount of material needed to be removed from the casting.
A hydraulic press forces the putty mixture through the orifices of the part. The putty naturally conforms to the shape of the casting and any outer surface material first before wearing down the rest evenly, all without distorting the casting’s original shape. This makes it perfect for complex interior shapes like intake manifolds, which can be a pain to shape with a standard die grinder.
If you are in need of more flow but are worried about gouging the casting or know the material is thin, extrude honing might be just the putty you need. Used this method before? Let us know about it in the Hagerty Forums below.