Do you have a lot of vibration? I've had water in the gas in our old Barracuda with 10.5 to 1 compression. The car would barely run if you tried giving it the gas. It knocked and backfired because of the high compression. In our pick up I got water in the gas and I thought that I had cracked the crank. The mechanics thought the same thing. Also, they thought the fly wheel was coming loose. I got the water out of the gas and it started running fine. A third time we actually had the electrode burned off in the Camaro we used to have. Our friend that delivers fuel, warned us that if there is a fuel truck filling the tanks at the gas station, don't buy gas there because he has the tanks all stirred up and the water isn't on the bottom of the tanks any more. Maybe this is a possibilty?