I just recently had my head taken to fix two bent valves. After putting everything back together i went to turn my car on and it didn't start. I did compression test and it was bad. Pistons 1,2, and,3 came out to the same compression of "100". The number 4 piston didn't have any compression. I know its not a bent valve because i just had the head rebuilt,new head gasket, and i did my timing right. What are the symptons of bad rings? Thats what i'm guessing it is. Has anyone ever heard of not having any compression and why?