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I keep saying that using aluminum heads is NOT an advantage over iron heads on today's lower octane gas, whether they are BOTH 8:1, 10:1, or 12:1.

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Go and try your hand at welding aluminum and then tell me that it doesn't have VERY different heat transfer qualities.

Detonation is caused by excessive heat in the combustion chamber. Because aluminum transfers heat away from the combustion chamber faster than cast iron, you are less likely to create the proper conditions to induce detonation.

Can you run a 10:1 motor with cast iron or aluminum, sure probably. Depends on lots of variables like cam, fuel octane and tuning. But all other things being equal, an iron headed motor is more likely to ping than an aluminum headed one.