On the way home from work tonight my car suddenly died, I was traveling in 5th at about 65 mph, once on the side of the road I tried to crank it to see what it would do, sounds like it has no compression, it does have spark and the cams are turning ( from what I can see thru the oil fill hole) any way if it is the cahin how difficult of a job and could I have done some valve damage? Thanks