The compression ratio is 10,04:1, pretty mild cam for the cui, 231/237@050, i have 18 hg/inch of vacuum at idle in park at 900 rpm, snap the throttle the gauge needle drops to 5 and bounces back to 25 and then go back to 18, the needle slightly floating within a half hg at idle. Im thinking that leaning out the carb more makes the 5 good plugs to running lean, like i said there is a rich condition in only 3 cylinders so the distribution must be uneven. Its strange, 5 plugs lookes really good and 3 to rich and the afr shows to rich, how can it be?