A method for installing a camshaft retrofitting kit into an internal combustion engine with a plurality of hemispherical combustion chambers in order to provide increased power. A variable camshaft timing (VCT) assembly and a plurality of displacement-on-demand (DOD) control solenoids are replaced with a VCT plug and a plurality of DOD plugs respectively. A performance camshaft is installed in place of a stock camshaft, and a performance camshaft drive assembly is installed in place of a stock camshaft drive assembly. A cam adapter may also be provided in order to extend the length and diameter of the performance camshaft. Additionally, a plurality of springs from a plurality of cam followers is replaced with a plurality of spacers.