when i got my car smogged a little while back, the place made me go get my timing changed because it failed because of that. so i wonder what the factory timing is, because they had me change it alot (from 25 to 18 i think. maybe the other way around). and right after i did that, i had a blown head gasket. i don't know if they're related or not though. should i get the timing changed back? and what does detonation really sound like? it sucks being a noob with engine stuff.