12.5:1 compression on pump gas???

[Project69]

I remember reading through a magazine, not sure which one it was, but it said it was possible to run 12.5:1 Compression on pump gas. It gave information about Cylinder head combustion chamber shape, it explained about what quench is, the total cc's above the piston at TDC etc. I lost the Article but if anyone has information on this that would be really helpfull

Thanks.