I use these on a set of #17 iron heads. They work. I know they are expensive but they are worth it. I only have four of the normal six exhaust bolt holes. Pontiac didn't drill the outboard protrusions to save money. I use Hooker manifolds with Remflex gaskets and these bolts. It's been three months and I still have no leak. Installing them takes time, but it's worth it. I fully recommend them for use with headers. My friend has a small block Ford and his ARP exhaust bolts keep loosening.