TORQUING HEADS

This month we’re talking heads, about one of the most feared engine misfortunes there is – a blown cylinder head gasket

- Peter Palm

Let’s be brutally honest. Ideally, the head and block should be as one to eliminate the pesky gasket. Unfortunately, this is far too difficult to manufacture as a single unit and is complicated by the block frequently being constructed from cast iron while the more complex head is made from aluminum. The advantages of an alloy head are much better heat dissipation and it is just a third of the mass of the older cast iron heads. By the 1960s to early ‘70s, most manufacturers had made the switch.

Withstanding the combustion pressures without any leakage is a daunting task for the lowly gasket and, to add to this, water and oil channels for cooling and lubrication also pass between head and block. To throw in further complexities, all components are in a continuous state of expansion and contraction – at different rates if the material properties differ – with heat build-up, then cooling down phases over the car’s lifespan.

DIAGNOSIS