17. The brass bushing simply slides over the post beneath the center cam. Pontiac originally used a section of thin rubber hose in many applications to limit advance, but deterioration over the years has caused many originals to go missing, subsequently allowing more advance than intended for the application. The brass piece is much more reliable. If you find it fits loosely on the post, a simple E-clip sourced from a local hardware store will secure it. The bushing can be installed without disassembling the distributor—we show it here in that manner for illustration purposes only.