by George Lyle
A billet is a simply a bar of metal. "Billet" parts are supposedly machined directly from the bar, without intermediate casting, forging, etc.
This method of making parts is more wasteful of material and produces weaker parts than other methods. Lots of stress risers and cuts across the grain of the metal.
So why are billet parts so desirable? In racing, many custom (one-only) parts are made from billet (the quickest way to make them) so many of the "trick" parts on a race car were "billet". Folks soon learned to associate "billet" with "trick" and the idea spread.
Many so-called "billet" parts really aren't made from billets. They are made from castings and have all exposed surfaces machined to look like a billet part. There's really no difference in quality or strength when this is done, despite what the advertisers in VW Babewatch will have you think.
All in all, the stock parts are probably stronger!