Sealing Cylinder Heads
In today's drag race engines (which are often combinations of aluminum heads and iron blocks), material expansion rates are much different. Aluminum expands about twice as much as cast iron. Because of this uneven expansion, a shearing action is created which can wreak havoc on the head gasket.
Head gaskets are one of those forgotten parts in an engine. If they work without complaint (and they often do) they get little consideration. They’re also seemingly simple devices. You just install the gasket between the head and the block, torque the fasteners to spec and it’s a done deal. Everything is bliss. Or so it seems. You see, when it comes to head gaskets, there might be more mechanics required than you first considered. Keep in mind, some normally aspirated drag race combinations use compression ratios that can approach and in some cases exceed 17:1. Those are honking numbers, but they pale in comparison to the cylinder pressures created by an engine fitted with a supercharger (belt driven or turbo) or one that’s bottle-fed. Sealing the works is absolutely critical. Here’s the inside story: