DIY machine work for heads??

You can buy a tool to neural the guides, or drill the old ones out,put chevy guides 11/32" so you can put chevy valves in little better flow with the chevy
parts.I'll post a pictures of the tools when I get back so you can see what they look like.

IF YOU ARE GOING TO DRIVE ON THE STREET ALL THE TIME YOU MIGHT WANT TO STAY WITH THE CAST IRON GUIDES.