The Choppers is a good b-flick. Junkman, done by H.B. Halicki, same guy that did the original Gone In 60 Seconds. He has another car flick too, but the name escapes me. Oh, and The Big Wheel is another old b-flick starring Mickey Rooney as a young racer following in his deceased fathers foot steps.
My all time favorite movie is Rebel Without A Cause, not a "car movie" persay, but its got James Dean and some nice rides in it for sure.
Theres a ton more, but I cant think of them right now. Ya have to dig around at the local Wal-Marts in the el cheapo bin for some of the obscure b-flick car movies. Thats pretty much where I always find mine.