Does anyone know the original height of a land rover cylinder head. I need to know if the heads have ever been surfaced or machined before. 4.2 14 bolt heads.. I plan to use a composite gasket. I read someplace that 37 thousandths is what needs to be removed to maintain my compression at - tin gasket levels with my newer composite gasket. But before I can do that I need to know what the head measured in the first place. I don't see it in the shop manual. where would this information be found?