Ratio rockers will open the valves deeper, for more fuel and air. But one must be careful....ala a high lift cam and a high ratio rocker can run the risk of ramming the valve into the piston. So it's a mathematical issue, of cam lift, plus rocker lift equals......what. and most builders will remove the head and putty the top of the cylinder, then hand turn the engine.......pull the head again, and check the putty to see how deeply the valve intrudes upon the piston. some builders will just use a thinner head Gasket to get an additional increase in compression
lotsa refined tricks for MO HP
Da Redflash