[jonnyk]

You may have to use shims based on the travel of the rocker arm across the valve stem. If the B303 has a smaller base circle than the stock cam, you may have to use a different length pushrod also. The best way to find out is to assemble it (correctly), and then turn the engine over by hand and watch the path of the rocker across the valve. You want as little movement as possible across the valve. It sounds tedious but if you do it right the first time, you won't have problems.