I had a Plymouth engine that punched through a gasket (don't remember which one) and allowed pressure from firing cylinders into the cooling system, over-pressurizing it and blowing coolant past the thermostat housing gasket. (Not to mention blowing holes in the aluminum radiator.) I'd think a perforated gasket would show up in your compression checks though.

I ended up with a new engine because the metal where the gasket used to be was eroded by combustion products.

Dave

Qui existimant se omnia scire faciunt vitam miseram nobis qui omnia valde scimus.