Thicker head gaskets/ less compression...

RustyRatRod,

Compression is heat.
You can run aluminum heads at a higher compression ratio and have the same -heat in the cylinder -as a lower compression steel headed engine because steel retains heat more then aluminum.

The compression ratio is what it is.

How much:
-Air-Fuel-Pressure-Heat = Octane required to prevent pre-ingnition.

Low octane gas---------:rolleyes: lol