What would be the consequences of say a 12:1 compression piston with say a stock B16 cam

of course the dynamic compression will be a lot higher than stock
would a higher or lower compression add/lose power, if the cam was not changed

don't give me an argument, that you HAVE to use more aggressive cams, I was just wondering the effects of "under cam'ing "

 

The only real neg effect could be that if u were running too much static compression, enough wouldnt be leaked out by the small cams, and high compression w.o bleeding off could result in premature engine wear.