I belong to the CobraClub.com and they have a similar forum. Lots of info about everything covering lots of cars. We send in $50 a year, get recognition as a donor, and that amount keeps the info flowing.
Basil, this is a business. Start treating it like one instead of a hobby and recognize that this forum is a service that a lot of people with common interests will pay to participate...that includes vendors, manufactures, classifieds, etc.
Closing it down throws away all of your past creation and efforts. You have developed a great foundation. Now it's time to build on it.
"Always do right. This will gratify some people and astonish the rest!" Mark Twain