13:1 Compression Pistons in 340 Small Block

Duane said

Aluminum versus cast iron heads
#7---Choosing Heads: Aluminum vs. Iron (Which Ones Do You Need?)

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I've read that. I run the same compression and timing on cast iron as I do aluminum. There isn't a difference. Run as much compression as your fuel, cam timing and tuning ability allow and disregard head materiel.