L78 & Today's Pump Gas?

[big gear head]

I'm running open chamber pistons. I measured the combustion chamber volume, head gasket volume and piston dome with a piston deck height of about -.005 and did the math. It came out to 10.99:1, which is pretty much 11:1. The open chamber shape and aluminum material may help. I also probably have more valve overlap with my cam than what a stock L78 cam has, which would lower the cranking compression.