Thread: 429 Help Please. It's A stumper

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Originally Posted by DennyW

You would actually need to know the month of that 1970. In 1970, is when they installed hardened seats. That was do to running higher temps for emissions. So, that engine may very well already have hard seats.

So with the hard seats I can leave the iron heads, correct?

Originally Posted by NightHawk

So with the hard seats I can leave the iron heads, correct?

If you have hardened seats you can run the iron heads with unleaded fuel, but if you opt for aluminum you can push your static compression ratio about one point higher without needing to boost the octane rating. The aluminum heads will dissipate heat faster, transferring heat of combustion to the coolant more efficiently, and if you're careful selecting the new aluminum heads you'll likely get improved flow, too.