Hey guys, I am considering buying these http://www.summitracing.com/parts/TFS-30300005/
But I have a few questions.. I am running a 78 350, 2 bolt block, with flat-top 4 eyebrow pistons..
When I did my calculations for compression with a 58cc block, I had somewhere along the lines of 12:1 compression..

What I've been reading about the aluminum is that an engine with cast iron heads with 10:1 compression burning 92 octane.. That if you were to switch them to aluminum it would run like it 9:1 compression.. Is this true?

 

It's the chamber size that affects the calculations.

 

You can get away with alittle more compression using aluminum heads rather then the Iron heads, for street car running 93 octane i wouldnt go past 11:1.

 

Compression ratio is dependent on the physical dimensions of the parts, it doesn't have anything to do with the materials.

An aluminum head transfers heat from the combustion chamber more quickly than iron, so you need to build the engine with a little more static compression to keep the output equal.