A few years ago I started playing around with making all Lego powered Scalextric Slot cars...and posted a few updates over in train tech as it's my normal hangout.
Anyway still building and refining the cars (and the trains) thought you might like to see.
The only non Lego part is the Scalextric Pickups, other than that, motor, gear and wheels are all stock lego and of course the cars need drivers and doors etc :)
There's loads more at: http://www.brickshelf.com/cgi-bin/gallery.cgi?m=dundarach
And on: https://www.youtube.com/channel/UC2WDMLO3euGHjdMr2XbgiJg/videos
Thanks, and I hope you like the idea :)