Many of the popular engine families utilize a positive stop type of rocker arm attachment, which does not allow for any adjustment and consequently there is no consideration for different cam sizes or other modifications to the engine block and heads. For that reason, COMP Cams has designed a kit to convert this setup to a fully adjustable valve train. On the 302-351W Fords, simply remove the standard adjusting nut, slip the spacer over the stuff, install the new nut and adjust the valves as necessary.