The car didn't do it till the night we raced Ray,on the way home we felt it and thought it was the clutch,well the new one's in and the vibration is still there.Compression is fine and no missing,I think it's a bent rod or a broke crank.The funny thing is no vibration and the car runs smooth as hell till 4000rpm,then it shakes real bad,almost like a spun balancer.