Educational Video that I found extremely helpful. DOHC 1.8 explained and broken down part by part.
http://www.youtube.com/watch?v=saPGX-1qC4M&feature=relmfu
Eric The Car Guy is a god lol.....I have been subscribed to his channel for a wee while now. Also recommend subscribing to briansmobile1 who has a load of good educational vids too http://www.youtube.com/user/briansmobile1