[Texasdoc]

My O2 sensor is only on one side - the passenger side. So, if it is not firing, it would be on the driver's side.

I don't think it is cross fire. I've re-routed the wires multiple times. I've ran the motor in the dark and don't see any sparking.

Pre-ignition - maybe. The cam isn't that big and I only have 9.5 to 1 static compression so I don't think my dynamic compression is very high. I'll have to study more about this and calculate my dynamic compression.

Valve float: I just got a valve spring compressor. I'm going to check the springs. There aren't any obviously broken springs but I may have a weak or damaged spring.

Edit: Dynamic compression 8.76:1