Water leaking out of head.

The front and rear holes in the heads go into a water passage. As if that's not bad enough, the wall thickness is thin. One Spring I took my car out of storage and went for a ride. Something let go when I was (ahem) clearing out the carbon and steam came out from under the hood. The header rear bolt had blown right out letting the coolant escape. Of course it was the one under the master cylinder by the steering column. Long story short, I took the heads off (wanted to that eventually anyway) and repaired the stripped hole with a heli-coil. I bought some studs at NAPA and thread-locked them in the 4 outer-most holes. Used stainless nuts in those locations. Been good for 6-7 years since then.