Jerry, its the seal material that has changed. The stuff that comes in kits is garbage! It won't hold together or hold its shape like the old asbestos stuff. You can't cut or pack it with out it falling apart. The stuff Best Gasket sells is like the old material with out asbestos added. I worked on a Stanley steamer for a couple years repacking and sealing valves. The material I used was form England and I suspect the Best material is to. It cuts clean with a new knife and requires no packing. If fact if you do pack it any at all, the engine will lock up, I did it! I have a dozen of them out running the streets and not one is even seeping!

Joe

1937 Chevrolet Inline-powered Streetrod