[jimberg]

When the head is O-ringed, it has a groove cut into it for each cylinder that goes with an O-ringed gasket. The O-ring is supposed to be stronger than a regular gasket.

I had a leaky heater core which was allowing my coolant to get low, so the head probably got a little warped. It's also something that tends to happen when you have two disimilar metals mated together that have different rates of expansion.

You should torque the heads exactly as they say.