Cam bearing oil galley restrictor reduces oil supply to the over oiled cam bearings. Set of 4. Can be used on street engines with hydraulic camshafts. Installs in number 1-2-3-4 main housing bore oil holes leading to the cam bearings. Knurling provides an interface fit. Use red Loctite. Measure depth of all holes before installing to be sure restrictor doesn't block the oil hole in the main bearing. Does not fit 403 engines.