Volume III, Issue 1, Page 18

If head gaskets work without complaint (and they often do) they get little consideration. They’re simple devices, right?  You just install the flat thing between the head and the block, torque the fasteners to spec and it’s a done deal. Everything is bliss.  Or so it seems. 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 power adder (belt-driven supercharger or gas-driven turbocharger) or one that’s bottle-fed. Sealing the works is absolutely critical. 

Why Are Head Gaskets So Important? 

According to a number of manufacturers, the gaskets between the cylinder head and the block form the most critical seal on the engine.  In a stock, high-output production engine, combustion pressures up to 1,000psi are common to normally aspirated gasoline engines while combustion temperatures will sometimes exceed 2,000 degrees F. In a race application, combustion pressures are much higher. According to Fel-Pro engineers, a GM-sponsored Winston Cup engine test generated combustion pressures in excess of 2,500psi! Obviously, the head gasket has to seal these forces.

In today's drag race engines (which are often a combination of aluminum heads and iron block), material expansion rates are much different.  Aluminum expands about twice as much as cast iron.  Because of this uneven growth, a shearing action is created which can wreak havoc on the head gasket. 

The head gasket must also seal coolant and hot (thin) oil -- both flowing under pressure between the cylinder block and the cylinder head.  According to Fel- Pro, this job is compounded because modern coolant formulas as well as oil detergents and additives tend to cling to surfaces and soak into gaskets.  Gasket materials are carefully chosen to resist these fluids and to maintain an effective seal. 

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