I'd start with a compression test, then pull the heads and see what it looks like inside. If you had good water pressure, you might have an obstruction in the block somewhere. Do you have a water temp gauge? Was water coming out of the tell-tale (pisser)?
If it's a chrome bore and you have cut through the chrome (broke ring, etc), then you will either have to have it re chromed or go to a steel sleeve. Otherwise, if it's just been smeared with alum, you can hone that out.