Why is heat treating a cylinder head dangerous?
Cylinder heads for four-stroke engines are by nature a complex design. The passages for the inlet air, exhaust gas, and fuel injection are incorporated as are the cooling water passages. These are normally manufactured from spheroidal graphite or nodular cast iron. Although not as strong as cast steel it is easier to cast and maintain reasonable strength under load. Of all the common metals, cast iron is probably the most difficult to repair when it fractures. However, it is ideal for engine cylinder blocks and heads because it is stable and relatively inexpensive.
Damage to cylinder heads may occur due to poor cooling which can cause thermal fatigue.
Learn about the risks of heat treating a cylinder head in our flyer.