I think it must be a secret. Try using the Search for 'nascar' - just in SD Cars. Word too common it says. So I try +nascar +category - still too common it tells me. Google Site Search finds 26 hits for 'nascar' on the whole SD community site.
Google only finds 1 hit for "category: nascar" and that's my post two up from here.
So I wish you luck with that one longtomjr.