Hello ! im new to all this ! joined in hopes of getting some input on my problem! so i own a 1966 Mustang Coupe Straight 6 engine. the other day i was driving to work going about 65mph and then my whole car started shaking , it felt like i had a blow out so i pull over (with my car still on) checked all tires which r brand new and everything was fine. i open up my hood and my motor was shaking hard! side to side! ....my father in law says it might be the head gasket? but were not too sure. Does anyone have any suggestions on this? i really appreciate it thanks !