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Is it OK to run aluminum heads on the street?



Of course! Most foreign cars have been running aluminum heads for decades. What gave aluminum heads a bad rap was the Chevy Vega and the way after market aluminum heads were surfaced. Aluminum expands almost twice as much as cast iron. A couple of decades ago (boy I feel old), all heads were machined the same way, with a slightly rough surface to grip the head gasket. Well, aluminum heads, with their greater expansion rate were actually skating across the head gaskets and the little machine marks left by the bits would cut, or wear through the gaskets. Now, when you look at aluminum heads, the deck surface is almost totally smooth so as the head expands, it doesn't scrape into the head gasket. The big advantage with aluminum heads, besides being almost half the weight of cast iron, is that they run cooler and allow you to run a little more compression (or cylinder pressure) on the same gas without pinging or detonating.

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